How can a teem build muscle at home?

I'm 16 years old and I really want to gain weight by gaining more muscle. I know how to eat right, but I don't really have the resources to body build. All I own are a stability ball, a pull up bar, and some really light hand weights (like 5 lbs). I don't have very much money, so I can't buy much more. Basically, how can I body build at home with equipment around the house, and what exercises should I do to gain muscle

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