If you're serious about this, I would recommend getting a YMCA membership or some sort of gym membership. Go with a friend so it's more fun. Start small, but gradually keep adding more weight. Start with 12 reps with a certain weight and move up to 15 over time. Once you can comfortably do 15, move up 5 pounds. Weightlifting helps you build endurance and get stronger.
Of course, if all that's too much for you, just look up some home workouts on the internet.