Ah. Most things can be found from any page, though the Forum is where RP takes place. There's a separate section for 1x1 and another for groups. There are also chat RPs, but I have zero experience with those.
At the top, you can find links to chatrooms. I suggest using those in firefox, since Chrome makes the whole page flash every few seconds and it's pretty hard on the eyes.
Also in preferences, make sure to experiment with the color scheme to find one that fits your eyes. I go with medium or medium light, though most threads rely on having a dark background color, so medium light doesn't always work, even when it's easiest on me.
Let's see, what else do you need to know? You can set 800x100 graphical banner ads under "My Ads" for free as long as they link to threads within Iwaku. Using those is a good way to get attention onto your thread by people all across the site.
Beyond checking the forums and making threads, that's all you really need to find RP here.
There's also a blog option that's a good place to store ideas, and a character gallery you can put characters up in. It looks like you found that. =)
Is there anything you need help with?
