Hi, welcome!
You probably got a welcome message via PM when you made your account. That's a great place to start. Depending on your comfort level, I would take a look at the various threads in the "interest check" sections. You can also browse the actual roleplay sections, and if you see one you like with a green "apply" or "jump-in" tag near the title, you can post in the OOC tab or message the roleplay's GM about joining.
Enjoy your stay!