well start reading the stickys and don't procrastinate on it.
Now what you can do in the mean time is take that big punching bag you have and start lifting that. I'm not joking. Start reading on how to do cleans, squats and overhead presses and incorporate that into your workout. It may not be the "conventional" workout but it'll work. I was working out over a vacation and all I had was a duffle bag and a bunch of sand and all I did was circuit training, one of the hardest workouts I've done. Also, do you not have a gym at your school?