The OOC forums are where most discussions take place (although some go to Skype or Discord), and it's where you post character sheets and other important out-of-character information. Every RP has different requirements and character sheets to use. Feel free to look through any of them that have been active in the past month, and you might find something you like.
For example, Titans: Reborn is an original superhero RP by the Doofiest of All, while Trials of Olympus is based on the Percy Jackson series. Since this is a Pokémon forum, there are also plenty of Pokémon RPs.
The IC forums are where all the actual content gets posted. The absolute minimum for IC posts is 100 words, but most people make posts a good bit larger. Don't be deterred by hilariously massive posts, as those are often "joint posts"—a single post made by multiple people.
I recommend checking out the Help Thread to get a bit of an idea of how creating and using a character works. It also lists some terms that are generally used derogatorily. A chunk of guides are listed in the thread, too.
At its base, you're going to be writing for one character in a multiplayer story. You're responsible for your character's actions, thoughts and perspective, like you're playing Fallout or The Elder Scrolls in writing form.
You might screw up a bit, you might need to remake parts of your characters before the GM accepts them (for reasons like continuity, balance, etc.), but chances are you'll make a few friends doing it.
Thanks for all the info. Still seems a bit confusing to me. So I think the first thing I should do is make a character.
Hi! Welcome c: The first thing to do is probably to check out the Roleplay Rules. How to find your way around the forums should be explained there, hopefully easily enough.
We usually make new characters for every RP we join (every thread is a RP in "Roleplay Casting" and "Roleplay Stage"), so people usually pick a RP to join first and create their character based on what they read there. Have a look in Roleplay Casting, I would suggest, and see if you find RPs that claim to have spots open. Ask the GM (usually the person who posted the thread) if you're unsure about a RP you find interesting - perhaps they'll let you in!
Once you're in a RP, I'm sure your fellow players will be happy to let you get into the swing of things gradually. It's a lot of fun when you get a good story going c: