Press in on the knob next to the pilot light and rotate it to the "Pilot" setting. Let the knob go.
Push that same knob again and click the igniter button repeatedly with the thumb on your other hand at the same time. The igniter button will light the pilot light, but it may take up to 45 seconds of repetitious clicking on the igniter button for the pilot light to ignite. Holding down the "Pilot" knob keeps the gas line open while you try to light the pilot, so it's important to keep that button fully depressed while you work.
Release pressure on the "Pilot" knob once the pilot light ignites. Wait two minutes and try again if the pilot light ignites then burns out when you release the "Pilot" knob.
Turn the "Pilot" knob to the "On" position once the pilot light remains lit after you release pressure on the knob.
Light your ventless gas fireplace using your thermostat, manual switch or remote control as you typically would.