Hi dimaria! If you want to learn how to play, then your best bet would probably be a newbie game. Just go to
this thread, type "/in newbie", and then wait.
It'll take some time before your game begins. The typical waiting period for a newbie game is somewhere around a week or so. (A little bit more.) That is a little bit high, yeah, I know, but we're working on that. If you have the patience to wait that long, you'll receive a role PM from the game moderator, and from there you're in your first game once you confirm your role. Your IC (and sometimes, SEs) can help coach you from there. Be careful and remember to read all the rules (in particular, about ongoing games). I know that games have a LOT of rules, and mechanics, which may be a bit hard to grasp at first, but trust me, you'll get them eventually.
As long as you're not violating the "don't talk about ongoing games" rule, you can still learn from various topics in this forum.
The stickied thread here gives you some of the more common questions you might have, and their answers. I'd recommend perusing other threads as well, since mafia discussion is a great place to see various different takes on what the game of mafia is.
Fair warning: as you may have noticed by the replies thusfar in the thread you made...mafiascum can have a lot of jerks. It is also filled to the brim with jaded cynics, who assume things like "alt" rather than "newbie who genuinely didn't know site conventions". (The two also have significant overlap, but are still separated in that there are jaded cynics who aren't jerks, and there are jerks who aren't jaded cynics, but usually the two do coincide.)
Still, welcome! Hope you can have a pleasant experience. You can
also introduce yourself here! <3