Welcome Tyrannis...
Hook up with an FSO squad that has open seats. Posting here like this is a great way to get started.
To answer some of your questions...
1) Yes and no. Historical battles are recreated, with the plane sets as close as they can get them with what we have to use. Objectives are issued to each side by the CM's for each frame. Then, orders and target assignments are written for each side by the CIC for each side for that frame. Then, squads come up with a plan to execute those orders.... be it attack, escort, or defend.
2) You can join a registered squad that is already in FSO, or... if you have friends that want to try FSO with you, you could start your own FSO squad. I would try it with another squad first though.
3) You can request axis or allies... usually, you get the side you want for the month. Sometimes though, there are just too many wanting one side or the other, and the CM's have to put your squad where they need to for balance.
Hope that helps some.