Open the valve on your propane tank very slowly. This is a knob located at the crest of your propane tank. If you open it too quickly, the propane supply will be cut off and you'll have to start again.
Plug the power cord on the heater into an extension cord with a three-prong socket. This should be at least 6 feet long to meet safety requirements.
Plug the extension cord into the wall socket. This should start the motor, which you'll be able to hear working.
Push and hold the automatic valve button on your heater. Continue holding it for 30 seconds. Depending on the model, you may also have a red ignitor button. You'll have to press this five to eight times to get the unit to light.
Adjust the heat to the desired level once the heater is lit. If the heater turns off, repeat Step 4 to relight the Coleman gas heater.