Hi Jamess,
On your control panel for the tanks you have 3 switches,,, Test,,, Pump,,, Heater.. The heater is for the water heater on propane. Make sure the propane is on and when the switch is turned on you will see a small red light come on also, but will go out when the heater ignites. If it does not light at first it will wait a minute and try it again. You might be able to hear the burner from inside the unit, but if you have never used it, I would go outside and you can feel the heat coming out of the burner vent.
Jim M