Insert the fireplace key into the key socket. Turn the key counterclockwise to ensure that the gas log's control valve is in the off position. If a knob controls your gas log instead of a key, turn the knob to ensure that is in the off position.
Light a log lighter or strike a fireplace match. Hold the flame over the gas log's burner, typically beneath the gas logs.
Slowly turn the key or control knob clockwise to release gas. Allow the flame to light the gas. Once lit, quickly remove the log lighter or match from the fireplace. Use the key or control knob to adjust the intensity of the gas log's flame.
Check the gas log's main gas supply valve to ensure that it is in the off position. Look inside the gas log fireplace or inside of the fireplace's access panel to locate the pilot light and pilot light igniter knob.
Turn the gas supply valve to the on position. Press or turn the pilot light's igniter switch to create a spark and light the pilot's flame.
Turn the gas log fireplace's control knob to manually adjust the intensity of the fireplace's flame. As long the pilot light is lit, the control knob may be used to adjust the flame and turn the fireplace on or off.