I had a similar looking furnace in my first RV. Lighting the pilot light in it was pretty much the same as on a home gas appliance: ensure the gas valve at the tank is on, open the pilot light chamber by rotating the metal cover, turn the gas valve on the furnace to "pilot", push the valve in while lighting the pilot with a long match or long lighter (preferred), keep the valve pushed in for 30-60 seconds after the pilot lights, let go and ensure the pilot is still on, close the metal cover, turn the furnace valve to "on".
Note that the propane gas to the pilot light will flow as long as the valve is pushed. Don't push this for very long without a match or a lighter going to burn the gas. Otherwise the gas will accumulate and can create an explosive mixture. It may take a long time to purge the gas line and get the pilot light. I found out that it is faster if you light the burners on the range first to help purge the air. As soon as the range burners stay lit, turn them off and light the furnace.
I highly recommend that you buy and install a carbon monoxide alarm before using the furnace.
2010 Nissan Frontier, 4x4, Crew Cab