Winterizing 2014 Minnie Winnie 31k question

I have a 2014 Minnie Winnie 31k that I am trying to winterize for the first time. The owners manual mentions a hot water heater bypass valve and a antifreeze siphon (winterization) valve. I removed the metal grate below the range and oven and I found the hot water bypass valve but cannot locate the antifreeze siphon valve. Without this valve I do not know how to get the pink stuff through the water lines. I thought I could just fill the fresh water holding tank with a couple of gallons, turn the pump on and do it that way, but I cannot figure out how to get the pink stuff into the holding tank. There is no fill valve or anything other than the city water and tank fill valves on the outside for when I am connected to water. Any help would be greatly appreciated!!!!