Yes you should purge the lines by starting your stove first, it helps get the air out of the lines or the furnace will go into a lock out condition for 5 to 10 minutes after 3 ignition cycles. All you need do is set your thermostat to "heat" and wait for it to light. you will hear a clicking sound by the furnace, that's the igniter trying to light the propane and you will hear it light off when it does ignite. My fan comes on first when I turn on my furnace, yours may too, so don't confuse the blower fan noise for the gas having been ignited. You will hear a definite whoosh sound when it lights. Make sure it is working before you go. After so long of no use it may need service.
