Yes, it looks like that wants you to pour antifreeze in your fresh water tank and then use that to pump throughout the camper.
A much better alternative (IMHO) is to install a fresh water tank bypass system....I'll see if I can get a picture to post. If you do a search in here, I'm sure there's lots of instructions already.
(Its a bypass kit that you attach right next to you water pump. When winterizing, you switch it and then run a hose into the antifreeze and then run the pump which gets it through all of the lines.)
Once you do it a few times, you'll only need 2-3 gallons to winterize.