The deck/set customization mode is a yellow option at the main menu that shows 3 cards to the left. When you go in here, you can set up diffferent sets of minions to use in battles. In order to do this, you must first play story or challenge mode and earn cards. Once you do this, simply go in to the set building mode and select one of the wheels. Highlight the card you want to equip, then flick the right stick in any direction and you'll see the small image on the wheel in the direction you moved the stick. Once you see it save, move on to the next one.
Repeat this 30 times for this for all of the trophies tied to this.