First, Welcome. Hey we were all new at some point.
Your water heater runs off two sources. #1 is propane and #2 is electric 110volt.
With your propane tanks turned on at the valves lite a stove burner to purge any air from the lines. Make sure your hot water tank is full of water by running a hot water faucet until air is purged or you could use valve on the hot water heater. Flip the switch on your control panel and that should light the hot water heater on propane.
If you are hooked up to "shore power" (camp ground power) you could choose to flip the switch on the hot water heater and heat with electric.
If you want to heat water faster turn both inside switch (propane) and outside switch (electric) on.
With the propane switch on you should be able to hear the burner and feel heat at the vent on the water heater.