If your question is where is the hose & valve to use to winterize.
You can get to it from the off door side storage compartment, on your right side you will see a small panel with 4 screws. After removing the screws you should see the hose for the antifreeze & the valve.
Or are you asking where is the bypass for the water heater, it is on the back side of it.
If you have an out side shower make sure you winterize that to. Good luck.
George.