I highly recommend you stick to the games posted on ASC.
You don't have to be a part of a team to play unless a specific game requires you to be part of one which is rare.
All you have to do is post that you're 'IN' then show up. Wear camo colours the host sets out in the rules and you'll be assigned to a group of people in which you can work as a team. If you're looking to join a team, read through the team threads.