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.