We have an Intertherm propane heater. What is the best way tolight the pilot light?

Very carefully. Actually the gas valve has a lever or knob that has to be moved into the pilot position then depressed. You will need a long lighter (I use a 24 inch butane model with a flex shaft) Then you light the pilot in the furnace itself.The pilot is located in the combustion chamber and is accessed through a small spring loaded access hatch on the face of the furnace a few inches above the gas valve on the right inside the burner panel.

NOTE: The gas line needs to be bleed first so gas is available at the pilot. Propane will pocket and GO BOOM if you do not know exactly what you are doing so You might be better having the propane company show you how to do it the first time.