You can google this and find tons of info, but here are a couple links for you. First, sanitizing your fresh water system:
This page covers a lot of things to look for when dewinterizing:
I'd caution a couple of things. Be sure your water heater is turned off if the tank is empty. They burn out quickly when empty. And learn how to bypass your hot water heater so you can avoid pumping gallons of antifreeze into it when you winterize. I learned that one the hard way!
Forgive me for the URLs. I haven't figured out how to create a link on this forum. But I hope these will help you. I'm sure the more experienced campers will have better information for you. Good luck and have a great time with the new camper.