To change your character's look you will need to access your Closet. You can access the Closet from the Home space (across from the level Portals) and in each of the hub spaces at the beginning of each land (except for Vault). After accessing the closet, you can tap on each of your unlocked items to equip them.

You can also view cosmetics you have not unlocked yet from the Closet, including the ones available in the Season Pass. To preview these items, you can tap on them as well. They will appear on your character, but will be removed from your character when you leave the Closet.