water fill and water heater
Filling fresh water:
Yes, the water tank is filled from the outside of the camper. The filler is usually close to the city water connection. It likely will be a hinged round cover about the diameter of a coffee cup.
I would start by hitching up a garden hose to the city water and opening the hot water faucet and try and get some water out of it. It may force out a lot of air before you get water out of the faucet. You can also lift up the safety release valve on top of the water heater and run the hose until water comes out the top of the tank. This will make help make sure the water heater tank is filled as it is possible to burn out the electric element if the tank does not have water in it. If you get water this way, you may not have to locate the bypass.
It sounds like you have located the water heater electric switch. If not, it is usually located on the water heater itself but can be hard to find. Some FunFinder models (like ours) have an electric switch inside the camper, but this switch may only be for the igniter when running the heater on gas.
2012 Chevy Silverado 1500 with factory brake control
Equal-i-zer 600/6000 hitch