You can change your character on the home screen of the game. As soon as you start playing, we will assign you one by default and, as you get coins in your games, you will be able to unlock the others.
To do this, you must tap the arrows that you will see on the sides of your character. When you see your favorite, you can unlock it by paying the necessary coins.
Keep in mind that you can play as many times as you want with any character that you have already unlocked.