You can change your player name and avatar at any time by tapping the avatar in the game screen's upper left corner. Once you do that, a ‘Player Profile’ menu will open. 

Player name — To change your name, tap the orange pencil located on the right of your name and type in the one you’d like to use. However, you can also automatically generate a new name by tapping the blue dice located on the left of your name.

Avatar — You will notice a selection of avatars located under your player name. Pick the one you like the most!

As soon as you’re happy with your name and avatar in the game, tap the ‘Confirm’ button to save the changes.