Coleman Gas Heater for home

I have a Coleman gas heater. My heat won't come on. I can here the blower comming on when I turn on the thermonstat. However no heat will come out. I went up in the attic and the heater instructed me not to light it with a flame. There was a yellow spiral kind of pipe with what look like a little yellow open and close valve. It looked like you should turn it and let the gas come in the heater from the gas line.I wasn't sure if it really was how to turn on the heater. I need some help. should I call the gas company or another company.