To change your avatar or name, you need to press the avatar on the left side of the screen.
 

If you want to change the name, you need to press the pencil button and type your new name in the text bar.

If you want to change the avatar, you need to press the avatar in the My Profile menu, choose the avatar which want to set and press "Save".
 
 
If you want to set your Facebook avatar as the game avatar, you need to link your game to your Facebook account. Then you will see your photo among other avatars in the game and will be able to set it as your avatar.
 
If you don't want to have your Facebook avatar as your game avatar, you can just set one of the preinstalled avatars.