So basically, you have Interest Checks, and roleplays. You find the level of writing you want, Free, Casual, or Advanced, and then you can check the interest checks section, either the general or writing-level specific ones, and see if you find any ideas that catch your attention. If that RP garners enough interest, the GM will head over to the actual roleplay section, whether it be a 1v1, Area, or any of the other three, and then posts whatever back story, information, or canon that pertains to the universe, and then GM will usually outline a character application skeleton for you to fill out and build your character, which can either be very advanced and list many different points of information, or simple and asking for the bare amount of information needed for your character.

Next, you wait and see if the character is accepted by the GM, and then you can post it the official character tabs for that particular roleplay, and then get working on your first 'In character' post.

Anything I should elaborate on?