I feel dumb for asking this but where is Squadron 42...I mean on my pc, how do I launch it!?

I have been playing for a week and im bored to death with the Arena Comander, there is much around my hangar I cant interact with and no doors lead anywhere. I've read post after post about what it is but where is it, is it somewhere outside my hangar, is their another program I'm suppose to launch, is it something I have to buy seperatly.

I feel like there's this whole universe somewhere on my computer I can't find and google, you tube and yahoo aren't addressing the Question I'm asking!