The water heater should work on gas or electric, or both. It works much faster on gas, the electric is much weaker. Make sure the tank is full of water, (open pressure relief valve with pump turned on) water should come out the relief valve. Also look for a switch in the outside heater compartment to turn on the electric element. Once it's on there, you can control it from inside the RV. The outside switch is to turn off accidental turning on element when the tank has been drained.
I would need more information about your water panel questions. Typically there is a valve to set water intake to 'City' and 'Tank fill.' City allows pressure from hydrant and connected hose, meaning you don't need to turn on the water pump. The other setting is to allow hose to fill water tank. Don't leave it on that setting, overfilling the water tank could cause damage. You might also have a control valve for winterizing or water heater bypass.
One further question: Why does your hot water need heating? It's a water heater, not a hot water heater.