In Classic:

Visit your Closet/Profile by tapping the three bars at the top of your game, then tap your Username to go to your Profile tab. To change your Profile image, tap on the Icon/image in the circle.

To change your username tap the pencil icon.

In Modern (Luxe):

Visit your Closet/Profile by tapping the Single Person Icon at the bottom of your game and then tap the Profile tab. To change your Profile image, tap on the Icon/image in the circle.

To change your username tap the pencil icon.