Instructions
Press "Square" in front of the pod computer, and then select the "Create" moon.
Start a new created level or load a previously created one.
Press "Square" to open the Popit menu above Sackboy's head.
Press "X" on the bag, which is the center icon in the upper row. A list of available costumes appear on the right-hand side of the screen.
Highlight any costume you want to wear and press "X."