Contact a professional and have him run a gas line to the fireplace if one isn't already installed. Licensed professionals are required by law in most areas to install gas lines into homes.
Remove the log grate and any wood log remnants from the Heatilator's fireplace floor. Sweep or vacuum the fireplace floor out with a shop vac.
Place the ignitor on the floor in the center of the fireplace.
Screw one end of the gas line to the gas supply line connection located on the inner wall of the fireplace. Tighten it with a pipe wrench.
Screw the other end of the gas line to the ignitor end and tighten it with the pipe wrench.
Place the log rack back into the fireplace and stack the ceramic logs on it.
Turn the gas supply line on using a fireplace key and then light the ignitor with a long lighter.