The one thing that I couldn't do in my 4 straight hours of PA was changing the commander... I heard one guy say that you were supposed to press the portrait on the start screen to change it? Not working. Is this just me or is that feature not in the game yet?
When you're at a published game where you can 'start' the game by clicking ready, if you click on the little commander image next to your name you can change which commander you're using.
sywynsam nailed it. Also. Do a search before posting. This isn't the first time this question has been asked.