Hi TexasAggie66,
Take a look at the diagram on page 6 of our owner-written
Water Systems Guide.
When you hook up to city water, the pressurized water from the spigot goes to all the plumbing fixtures. The output side of the water pump is teed into the same lines going to the fixtures.
To fill the fresh tank, it depend whether you have a gravity fill, or a 4-way Anderson Valve. These are explained on pages 7-9 of the guide. If you have gravity fill, the water hose from the spigot has to be connected to the tank fill inlet. If 4-way Anderson Valve, the valve selector must get move to the TANK position to fill the fresh tank. There's only 1 water inlet fitting, so the hose connection point is the same as when using city water.
Fresh water tanks are usually located above the axles. Look on the off-door-side, just in front of the axles for a short piece of PEX tubing hanging down. It'll have a valve control used to drain the tank.