Here’s how it works: you go to play.dmzcraft.com, and type /skyblock. You’ll be ranked as a guest, and have no permissions to build (so you can have a look around!). Spawn contains teleports to all the islands, arranged in quadrants (Easy, Medium, Hard, and Extreme — the layout of spawn mirrors the arrangement of the islands). The available islands should be marked with an end rod, but you can also check the dynmap to make sure. When you’ve found an available island in your preferred level of difficulty, submit this application, including several sentences (a paragraph, even!) about who you are as a Minecrafter — how long you’ve been playing, what kind of server atmosphere you like — and if you’ve got skills that might be useful in contributing to the ongoing development of this server, by all means mention those too! I’ll get back to you as soon as possible, but I do work, so it may take a wee while.