Nope.  You just have to send an invite.  As soon as I sent it to you it said that the three uniforms were unlocked.  You don't even have to accept it.
It's a lot of fun, but I noticed a couple things wrong.  First, the hurry-up.  I was playing as Oklahoma against Texas and was down a TD.  A couple times I tried to push square to call a hurry-up, but each time the game was showing the replay.  The first time I held the square button but was taken to the play-call screen after the replay was finished.  The second time I tapped the button through the replay with the same result.  This needs to be fixed.
Another problem seems to happen to receivers who get bumped by a blitzing DB.  I was in a four-wide set and called a HB Flare.  A slot receiver has a post route.  That receiver got bumped by a blitzing corner and stopped.  He was just standing there throughout the play.  Not good.