Boondocking for your first camping trip...
First, the fridge should have a knob (if it's original) with "GAS" and "ELEC" printed on it. Turn it to "ELEC" to turn on the electric element. Turn it to "GAS" for LP. The LP tank needs to be turned on for that to work. On the back of the fridge is a valve to hold for the pilot to light, you'll need to hold the valve up to start the gas flow. I'm assuming the little flint wheel doesn't work (they seldom do). Hold the valve up for at least a minute after ther pilot lights, then release it.
The grey and black water should be easier (just messier). Hook the blue tote to the spot the black tank dumps into with the sewer slinky, using the fittings that should be on the hose. Make sure the black tank dump valve is closed. That will be the only valve, and should be in the rear compartment.
I'll stop here so you can find what I posted about.
You'll also need to know about hot water, water pump, vent fans, lights, not using much water or battery power, but I don't want to overwhelm you.