The little diagrams by the knobs in the top right corner tell you how they need to be positioned for different uses. Right now it is set to use from a city hookup with both knobs vertical, which I see you have the hose connected. Turning the right knob horizontal and left knob vertical allows you to fill the on board fw tank. Turning the left knob horizontal and the right vertical is for using the tank.
Dwayne and Susan
Jiro and Phoebe-4 legged family members
Mike and Dana - Traveling buddies
2016 Ford F350 XLT 6.7 Powerstroke DRW 4X4
2016 Brookstone 395RL