So you preordered Resident Evil 0, eh? And now you want to change into those spiffy costumes you got for preordering the game, hmm? Unfortunately, the game is shockingly obtuse when it comes to the simple act of changing costumes for your characters, so don’t worry if it isn’t apparent right away.
What you have to do it go into your character’s inventory and highlight the character’s personal item. For Billy, it would be his lighter, and for Rebecca it would be her mixing kit. Click on the personal item and hit the ‘Switch’ command. This will allow you to swap out their personal item for a suitcase. Highlight the suitcase and click Use, and this will give you access to all the costumes you currently have in their arsenal.
And there you go. That’s how you swap costumes in Resident Evil 0. Remember to switch back to your character’s personal items once you’re done changing their costumes.