How can I gain muscle m?

I'm a 13-year-old. I weight about 105.6 pounds and am 5'4". I know I'm not overweight, but I have a lot of fat on me (the squishy kind). I swim every week and do yoga twice a week. I've been eating more fruits and vegetables and less junk food. What else can I do to gain more muscle m without having to buy exercise machines?