You should have two battery systems that are separated from each other. the Chassis battery should be under the hood and starts the engine and powers turn signals, dash heat, wipers, driving lights, etc. The House battery is somewhere else and powers everything in the living quarters of the RV.
Important to note that the House battery powers the refrigerator to switch between LP gas or 120 v when connected to shore power or generator. The thermostat is 12 v and controls the furnace which is LP gas and 12 v fan, and the thermostat also controls the roof air conditioner when connected to shore power or generator. The water heater is also 12 v controlled with LP gas burner.
On the dashboard there might be a 'Boost' switch that when held down will connect both battery systems together to aid in starting, sort of 'jumper cables' but you don't have to go under the hood or connect to another vehicle.
You should have 3 tanks, a fresh water tank, a gray water tank, and a black water tank. The gray water is from sinks and shower, the black water is from the toilet and may also have the bathroom sink connected to add more water to dumping the black tank. You typically dump black tank first then use the gray water to flush out the drain hose (called the 'Stinky Slinky')
Your fresh water hook up may vary, but typically you'll have a hose connection that you can use to connect to a hose bib and use the city water to pressurize your water system so you don't need to use the water pump. You might have a second opening on the outside of the RV that allows filling of the water tank or perhaps just a valve that switches between 'City' and 'Fill' If you have a single connection for both functions, be sure not to try to pressurize the RV water system through the water tank. The pressure can expand the tank until it causes structural damage or bursts.
Here's a link to a '85 Jamboree owner's manual, it says it's for a '85 Class C, but it has some illustrations that show a Class A. http://fleetwoodrv.com/partsandservi...5_JAMBOREE.pdf
I found it at:
Fleetwood RV Parts and Service