[quote=DeathstrokeSW]
So, whom do I talk to about joining squads?
[/quote]

Well, I believe the first page has a list of the filled captain slots, I control Ryan, so if you were looking to join Squad 3, I'm the one you speak to, otherwise, it should be in the list, if there's no captain for that particular squad, talk to another one of the captains, and they'll get you into that squad (and get your missions from those other captains as well)