Go to a real boxing gym (if there is none where you live you'll probably have to drive a ways) and train for a few months. Most have one hour classes of boxing workouts as well serious competitive training, all taught by boxing coaches.
Then if you want to get seriously into competition you will need a boxing license and start training twice a day, usually some running and weights in the morning and then specific work at night like bagwork, sparring, etc.
I have played virtually every sport in my life and IMO, boxing is the most brutal, violent, and exhausting training, hands down.