How do you equip combo cards in Sonic Battle

When you are in the map area, like Emerald Town, and the other places, not during a battle, press the Right Trigger. Then go to Edit Skills, and go to the Attack column and find Ground Power. Then, just pick which Combo Card you would like to use. Personally, I would suggest Sonic Combo. He does a series of punches and kicks and, lastly, does a Sonic Wave (I think that is what it is called, not positive though) which helps dodge E-102r's explosion.