When I am done camping am I supposed to drain the hot water heater? If so, how do you do so?

No. You don't need to drain the water system unless you are winterizing. It is actually better to keep the water system wet. The water could get a little funky after sitting for 6 months or so but flushing it with fresh water then sanitizing the system with bleach water is all you need to do.

Except as part of the winterizing procedure. There is usually a nylon drain plug that unscrews. Make sure you have the pump off and a faucet open and the water is cold. I undid it with it pressurized once it shot my socket wrench across the driveway and sprayed me with water. Very unpleasant in October but luckily no witnesses.