I haven't really rped before. I kind of wanna try it out. How would I start here?
You've got a lot of options!
PC's roleplaying section is divided into
Out-of-Character (OOC) and
In-Character (IC) forums.
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.