Hello there Hermione!
The mods create a Newbie's Guide to help new players. You can find that here-
the-newbie-guide-roleplaygateway-read-this-first-t2769.htmlBut I would suggest the best place to start is to click on the Roleplay tab on the top of your screen. It'll take you directly to where all the RPGs are.
Under the Forum tab, there's the Out of Character (OOC) Forum where you'll find 2 threads of Roleplayers Wanted and Interest Check. In the first one, you'll find list of RPGs that need players. The 2nd one mentioned is where Players talk about what kind of rpgs they want to create. It's also where players advertize for RPG partners (1 x 1 private rpg).
Here's a link to the General rules of the site thought-
rulesIn RPGs, GMs (General Moderators) of their particular games are allowed to make their own rules for them (as long as they don't break the rules of the site).
If you have any other questions, don't be afraid to ask. Hope this helps and have fun!