Most roof AC units do not have heat. Most likely you have a gas furnace. To run it, turn on the propane, switch the thermostat to heat, and set the temp high enough for the furnace to cycle on. If it is the first time it has been used be prepared for the smoke alarm to go off as the furnace burns any protective oil on the internal sheet metal.
2013 JayFlight 26RKS
2013 F-150 SuperCrew XLT w/EcoBoost, 4x4, 3.55 E-locker,
firestone airbags in back, windbag behind the wheel,
E rated Michelin LTX M/S2s
"No matter where you go, there you are"