You're right. It should be a simple process. But...
Have you successfully started any other gas appliances? If not, there could be air still in the lines or the gas isn't turned on. If there's air in the lines, get your stove to light first, then try starting the furnace.
When you start the furnace, the fan should come on immediately (there's no wait time like the forced air gas furnace found in homes) blowing cold air. Does it? If not, check your thermostat to ensure you have it set to Heat and the temperature is set high enough for the furnace to come on. If that appears to be ok, check to see if the fuse for the furnace has blown.
The furnace runs on 12V DC so as long as the battery has sufficient power, it should run.
2009 GMC Sierra 2500HD | Crew Cab | Standard Box | 4WD | Duramax/Allison
2000 Jayco Eagle 266 | FBS | TT
1986 Coleman Laramie pop-up -- Still in the family!!!