This doesn't look like an electronic ignitor system, but rather the old microvolt type. If so, the white horizontal knob should say something like off-pilot-on. Turn to pilot, and push down. (there will be some sort of temporary position that must be held against a spring-load). You are then letting propane get to the pilot light, which you light manually, with a butane fire stick. On yours, stick the light inside the hole in the box on the right. Pull out the stick, and you should see the small blue flame of the pilot.. If so, CONTINUE TO HOLD the button down for about 30 seconds. The pilot will warm a thermocouple, which will generate a small amount of electricity, enough to hold the valve open by itself. Then, let go of holding down the button. Check pilot again. If it's on, you're golden. If it goes out, repeat. Once it is on and stays on, turn knob to "on". The main valve should open, and the main burner should light. The pilot stays on all the time; the main burner turns on/off dependent on cooling need. (yes, boiling the ammonia chemical produces cooling). If you turn everything off, or shut off the propane, the pilot goes out, and you'll have to repeat from the beginning.