You say it’s a pillar, but it’s more like…a thing that more than a few players enjoy and most of the rest of community equates to erotic roleplay. If it were an actual pillar of the game, we’d see more being done for it and to accommodate it. At best we’ve gotten transmogs, the barber shop, and some in-game towns and cities built with the idea that RP could happen there. But there’s really nothing the development team does or has done to facilitate or create RP in the game. That’s a completely community-driven aspect of the game.
That said, like most hobbies, you should start by doing what’s most comfortable for you. That can be reading about something, going and observing it for a bit, or just jumping right in head-first. I would not recommend the latter, however, because most peoples’ first forays into RP tend to involve making a lot of mistakes and alienating or angering a lot of people in the process. It isn’t ALWAYS like that, but experience has told me this is often the case.
Check out the Lore and World’s End Tavern forums. Read the forums for the RP realm you’re looking to join. Go and spend some time on the server watching how others interact, and if something looks like fun to you, chat with the people in tells or sign up to an RP guild. Not everyone will be receptive to chatting in tells, by the by.
Most RP servers have a discord or three you can check out, and nine times out of ten, if you ask on the forum there, people are going to be more than willing to help you out and direct you to places and resources that will aid you in your journey.
WoWPedia is your friend.
Also, if you’re into writing and want to chat with some like-minded people, we have a discord called “Writers of Azeroth” which you are more than welcome to join. It’s not real noisy, but newcomers are always welcome, and everyone there seems to be genuinely interested in helping out others–especially with RP issues or questions.
Like most groups of people, everyone has their idiosyncrasies. Not everyone is going to like or want to be a part of certain types of RP. And that’s fine. And it might take you a while to figure out your own likes and dislikes, and that’s okay, too.
And if that all seems like a bit much all at once, feel free to take it slowly.
One of the best ways to get involved in RP is to find a guild with an RP concept that interests you and join them. You may find it clicks for you. You may find it doesn’t. But it’s one of the better ways to learn. Also, …don’t be afraid to ask questions–even if you think they’re dumb. Or someone at some point said that was a dumb question. We all have to start learning somewhere. And maybe the “dumb” question will help you to learn better questions to ask.
TL;DR:
Treat it like you would any other hobby. And have fun. 