As others have said, this is not a gym. You might be a little young right now to join a gym, but some do let you join at age 12. Did you talk to your parents about this?
Very cool, Ben. I agree with the idea of getting your parents to help you. Maybe you could find a gym to go to together. Rec Centers are a good place to look as well. I have worked at several rec centers where I have lived to give back to my community. There are always lots of fun fitness things to do there. And the trainers at rec centers seem to work with a lot more people in your age group as well.