to the forums. As Windrider stated, makes and models differ from time to time but here are a few things that apply no matter which year or model you have. First for any of these appliances to work on propane you need to be sure the LP Leak Detector is switched on. It will chirp when first turned on and then a green light will blink. This enables the solenoid valve at the propane tank to open so propane can go to the appliances. Be sure your propane tank is turned on and you have propane.
As for the furnace, set the selector switch on the thermostat to heat or furnace [it may have one or the other] then set the temperature you want. The inducer motor should come on and then the ingitor should spark to light the burner. As for the water heater, first make sure you have it filled with water. There should be a switch inside usually near the rest of the monitors for the water tank and waste tanks. Turn to on, there's usually a light indicator next to it. It will light briefly until the burner lights, then it goes out.
Good luck and once you provide the exact info I'm sure we can help you get going.