The gas cylinder (11kg) is located under the bed in the rear. (Fold up the front half of the bed and remove the plastic cover). To turn the gas cylinder on or off, turn the brass-coloured control knob to + or -.
When cooking, be sure that the gas cylinder is open and there is a red lever in the cutlery drawer in the kitchenette that needs to be turned horizontal (vertical=closed, horizontal=open). Turn on the gas at the cooker and ignite it with the black knob.
Caution: Be sure to close the gas cylinder before driving!
Here is a video (in German) for a better overview: