you don't know how to play a game you've never played before? Gosh how stupid! :V
But really, I'd suggest looking at the Round 30 topic, look over the first few posts by the GM and it should give you a pretty good idea. Don't worry too much about memorizing all the abilities, because that'll kill you before you memorize it if you've never played before.

Also, just watch a game going on, it shoudl help you figure things out.
There used to be a more helpful paragraph or two in the mafia topic posts that explained the game flow more, but it's since been taken out I believe. D: