There will be a "draft" next month. You pick your players (by position and availability) and form your "team".
Once that's done, the season begins (All games in Fantasy are based on real ML games). Although your players may be from different teams, it is important to set a lineup based on games that will likely feature your players. This may have to be done either on a daily or weekly basis.
Stats are complied based on the actual stats of the players. You win or lose based on the categories selected (Atari hasn't announced them as yet).
It gets easier once you're in. Of course, other members of the league will always give you advice if needed.