A motor home has two basic water systems. One is directly connected to campground water system. Often it is referred to as “City Water”.
The other is a holding tank with a 12 volt water pump that you fill from a campground tap.
Both systems feed into the same plumbing system.
Fresh water holding tank system:
If you are using a garden hose, you should use the holding tank system and disconnect the garden hose. You need a “potable” water hose for safe household water. Potable water hoses are usually white in color. Ordinary garden hoses will leach chemicals into the water.
Flush the garden hose well. Then connect and fill the holding tank. Next, disconnect the garden hose. You would not have to disconnect the potable water hose. It will not leach hazardous chemicals into the water.
There are two basic systems for filling the holding tank. One is a fitting on the outside. You insert the end of the hose into the opening and turn on the water. Turn the water off and remove the hose when full.
The other is through a valve in the water bay. Connect the hose to the “City Water” garden hose fitting. Set the valve to fill the holding tank. Shut off the water and remove the hose when full. Return the valve to normal position.
City Water System:
After the leak you mentioned above is fixed you can leave the potable water hose attached until outside temperature drops to freezing. Make sure the holding tank fill valve is returned to normal position otherwise tank will overflow and water will spill out in various places.
Cold Water Plumbing System:
The cold water plumbing system is simple enough. It is pressurized either by the 12 volt water pump or through the City Water hose connection.
The 12 volt pump has a switch on a control panel inside and possibly another one in the water bay. This system has a filter on intake side of the pump that can become clogged.
The pump runs only when a faucet is “on”. It may also run for a while to fill the 6 or 12 gallon water heater. If it runs continuously, something is wrong. Shut it off and trouble shoot.
The City Water system is intended to be connected to the campground water system long term. It has a “garden hose” fitting. It needs a white potable water hose to connect.
There is a screen in the garden hose fitting in the water bay or on the outside of the RV. The screen can become clogged. Pry it out and clean it if necessary.
Next there is a check valve behind the screen. Sometimes the valve can become stuck. I can see mine when I remove the screen. Gently poking the valve can loosen it.
Some RV owners install additional filters inside the RV. No telling how it works without pictures and possible owners manuals.
Hot Water:
The hot water side of the plumbing runs off of the cold water system. So if the cold water does not work, the hot water won’t either.
There are different hot water heater designs, so make and model are necessary for us to give good advice. Some have pilot lights. Some have electric ignition. Some have 120 volt AC powered heating elements. A post above says you have a pilot light type heater.
Make sure the water heater 120 volts AC is turned “off” until you are sure the water heater is full of water. The AC element will melt if it is not immersed in water. There will be a switch on the control panel to turn the AC water heater on or off. There may be another switch to turn the water heater gas burner on or off.
There is much more to learn, but hopefully this is enough to get your water system working.