TO BE UPDATED: The main Aether II launcher is down as of now, so this guide will cover how to manually install Forge and the Aether II in the beginning section (until further notice).
Getting started in The Aether II is a lot harder than starting in the first version of The Aether. There are more mobs you need to be aware of, and a lot more features to take advantage of. However, there are also fewer Dungeons to get items from. We shall give you tips on how to survive in the following paragraphs.
Manual Guide (1.7.10)
Open up the Minecraft launcher and create a new profile. Name it whatever you want but make sure the version being used is 1.7.10. Let Minecraft launch fully to download 1.7.10 then close it. Next, download Forge from here and run it. Select "Install client" and hit ok to let it install. Start up Minecraft again, select the new "Forge" profile, launch Minecraft and then close it when it finishes.
Open up the main Minecraft launcher. In the bottom left, click "New Profile". Name it whatever but preferably something among "Forge" or "AetherII", but important is "Use version:" in the middle. Set it to "release 1.7.10" as a base for Forge, and save your profile then close Minecraft once you launch it to get the needed files loaded.
You'll need to download the Aether II mod, and make sure to drop them into the 'minecraft\mods' folder and where depending on your OS below. Run Minecraft to make sure it launches Aether II correctly.
OSX: ~/Library/Application Support/minecraft
Getting Started in a New World
When starting a completely new world with The Aether II mod, you first want to play regular vanilla Minecraft. Collect materials, survive, etc. Your first objective should be traveling to the Nether. When in the Nether, try and find Glowstone. It will usually be hanging above from the ceiling of the Nether, but sometimes you are able to grab it when the ceiling hangs low. Glowstone is the material that you make the Aether Portal with. You must grab at least 10 blocks worth of Glowstone, or 40 Glowstone Dust or more. Make sure to grab not just forty Glowstone Dust, but make sure to craft them into Glowstone blocks like this:
Once you have gathered some Glowstone, you are going to need a Water Bucket. This is the ignition to the Aether Portal, much like the Flint and Steel (or, any sort of fire in general) is for the Nether. Then, build your regular portal frame (it's the same portal frame as a Nether Portal), like a Nether Portal, you can leave out the corners and still activate the portal, causing the total Glowstone blocks to be 10, instead of 14. Once you have finished the portal frame, dump the bucket of water into the bottom blocks of the portal frame and it will ignite into a swirling blue portal. Entities are also able to go through the Aether Portal, like the Nether Portal.
Get ready, because many more challenges await you in this mystical dimension!
Now in the Aether
When you first spawn in the Aether, your portal will most likely (if not always) be on an island. If not, you may have ended up spawning on a tiny island or a chunk of land only a few blocks big and surrounded by a whole lot of literal nothing.
Take note of your surroundings and gather Skyroot Logs to make your standard wood tools. You will most likely find Zephyrs, which are flying mobs that shoot gusts of wind at you. These projectiles deal no damage, but have a big knockback effect which will launch you in the air. If you fall off the Aether, you will be teleported back to the Overworld, and depending on your current co-ords in the Aether, you will die instantly from fall damage unless you're saved by a sufficiently deep body of water. If you were far away from the portal when you fell though, you may land in a completely unfamiliar place, so take caution.
Next, you want to gather your basic Aether materials. Trees are incredibly common in the Aether, they're almost everywhere. In fact, there are no biomes in the Aether; it's all one, similar to that of the Nether. When harvesting trees, you will sometimes encounter Skyroot Log Walls, which are basically the roots of trees. These cannot be made into Skyroot Planks like regular Skyroot Logs can. These are purely for aesthetic purposes, aside from having the function of normal Cobblestone Walls. You may notice a variety of tree colors, but aside from the pastel shades of leaves, these trees do not differ. There are three types of trees: The Golden Oak Tree, the Skyroot Tree (which comes in many colors of foliage) and the Crystal Tree. All three types of trees drop Skyroot Logs, so do not be overwhelmed.
Once you get Skyroot Logs, make them into planks, then four planks into a Skyroot Crafting Table. There is no difference between the vanilla crafting table and the Skyroot one, besides their texture and name. Place down the table and make your basic Skyroot tools. As you go on, you will need to upgrade to better tools, so gather Holystone. Holystone is the block that substitutes for Stone in the Overworld. Mining in the Aether can be really dangerous. Don't dig too far down, or else you will fall through the bottom of an island and fall to death. When mining, you can find many different ores.
Normal torches function in the Aether but since Ambrosium is your only primary fuel source for light, you will need to rely on Ambrosium Torches. Ambrosium can be gathered from Ambrosium Ore, which is, in simple words, the counterpart of Coal in the Aether. To make Ambrosium Torches, put an Ambrosium Shard over a Skyroot Stick, and it will give you eight, unlike regular torches, which gives four.
There are several new types of food in the Aether. Across the landscape of the Aether, there are bushes that have a berry texture on it. The bush is a Blue Berry Bush. These can be easily farmed, and they're a really efficient source of food, replenishing two hunger drums. You may also find the somewhat taller Orange trees. They're like a slightly better version of the Blueberry, replenishing four hunger drums. You may want to start with Blueberry farms, but eventually upgrade to an Orange farm. Orange plants can grow up to two blocks high, unlike the Blueberry bushes, which only grow one block tall, so may sure to have enough clearance if your Orange farm is indoors.
Also, Holystone can be turned into a Healing Stone using an altar and two pieces of Ambrosium Shards as fuel. Occasionally in the Aether, you will come across purple and blue trees with white specks on the leaves, this is a Crystal Tree. When the leaves with white specks in them are destroyed, they will drop a White Apple. These do not replenish any hunger, but will temporarily stop any poison effect the player has for four seconds.
Once you have acquired some basic Holystone Tools or Skyroot Tools, it's time to gear up. You can try to start a mineshaft as you would in the Overworld, but this can be dangerous as you may fall out of the Aether. You can also explore the Aether, looking for stray ores that are visible from the surface. A better way to find ores is to build scaffolding down to a patch of Cold Aercloud, which are white, and look up at the underside of the island to find rarer ores, and then build your way over to them. There are four ores you found in the Aether: Ambrosium Ore, being already introduced to you, Zanite Ore, and Gravitite Ore. Continuum Ore can be found in dungeons (as orbs), but can rarely be found on island undersides.
Zanite Gemstones, which are dropped from Zanite Ore, are the equivalent of Iron in the Overworld but tools, armor, and weapons crafted from it become stronger when lower on durability. Continuum Orbs produce a random item when right-clicked, and can be useful by giving you high-tier items early on, but may sometimes give you Overworld items such as Blaze Rods. Its ore is the rarest among the four ores found in The Aether, and is the only new ore introduced to The Aether II. Gravitite is the equivalent of Diamond Ore (note that it only does as much damage as an Iron or Zanite Sword) in the Overworld and allows you to jump high and throw monsters and blocks high in the air using the tool specific to that item. However, its ore floats up instead of dropping, which means if it were to be placed on the ground with no obstructions above it, it would fly up and be lost.
Before entering your first dungeon, it is recommended to have a full set of Zanite Armor, tools, Healing Stones, and possibly a Gravitite Sword, Dart Shooter + darts, and a Gravitite Pickaxe, the latter specifically for the Slider boss. A good food is recommended. (Blueberry Lollipops have a good cost/benefit ratio compared to Enchanted Berries or Rainbow Strawberries, and all three ingredients (sugar, blue berries, and skyroot sticks) are easy to acquire in bulk + are all renewable)
Exploring Dungeons: Slider's Labyrinth
Now that you have a set of Zanite tools, it's time to find your first Dungeon, the Slider's Labyrinth! Explore the terrain for medium stone towers with blue glyphs. In these stone structure,s there'll be a glowing and rotating blue totem. Right clicking on the totem will teleport you to another dimension where your own dungeon will be generated for you. If playing on Multiplayer, it might be a good idea to invite some friends to help you. When in the dungeon, you will encounter Sentries, Sentry Golems, and Mini-Bosses. Destroy the Sentry and Sentry Golem spawners quickly, and loot the chests for Zanite, Continuum Orbs, Poison Buckets, Gummie Swets, Wheat, Pork, Oranges, Gravitite blocks and Music Disks. You can leave the dungeon and come back later any time if you run out of supplies. To conquer the dungeon, you have to find all three mini-bosses in the dungeon and defeat them. After doing that, go to the boss door (most of the time it is next to where you spawn). Right-clicking it when you have all three key shards from the mini-bosses will open it up, revealing the final boss room. You can return to the dungeon after conquering it but there'll be no new Slider or mini-bosses. After killing the final boss, Slider, he will drop a ton of coins and loot. If you're in a party, the loot is per player, so everyone in your party will obtain loot!