Whenever your child completes a chore and you approve it, they get a ticket to spin the wheel in the Monster Carnival. If a "CLOSED" sign appears, it's either because your child has no tickets. When your child spins the wheel they have a chance to win a Monster or a consolation prize. If they win a monster, that monster will be kept in the "Monster" section of the web or mobile app.
Your child also has the choice to save their tickets. By saving them they can pick out a monster that they wish to earn instead of a chance to win one.