Gas fireplaces can provide many of the benefits of a traditional fireplace without the need for procuring wood and cleaning up fireplace ash. Because a gas fireplace is tapped directly into a gas line, certain precautions must be taken for safety, and certain aesthetic features of a fireplace are added artificially. Installing the embers and rock wool is an example of this, as these are the components that give a gas fireplace the look of a natural fireplace with its burning embers.
Ensure gas is turned off at the fireplace valve. This will be turned back on after the rock wool and ceramic logs are correctly placed.
Ensure that the gas fireplace is correctly and safely installed up to the point of placing rock wool under the ceramic logs. This includes ensuring the burner pan is safely capped at one end and connected to the gas line at the other, as well as the pilot and diverter are correctly assembled.
Spread sand over the burner pan, being careful to not cover and clog up the pilot.
Put the rock wool over the sand and burner pan, being careful to contain it to the area where you will be placing the ceramic logs later. This is important so there isn't a messy appearance of embers outside the "burn area" of the logs.
Cover the entire fireplace floor area with lava rock, which is usually included with the ceramic log kit.
Place the grate over the burner pan area.
Arrange the ceramic logs on the grate in an arrangement that looks like logs in a natural fireplace. Refer to the manufacturer's instructions for how best to arrange them -- these instructions should have come with the ceramic log kit.
If a hissing sound is heard from the burner pan, check that the sand is spread evenly over the burner pan. To check for gas leaks at the connections in the system, liberally apply a soapy water spray to the connections and watch for bubbling.
Be absolutely certain that the gas source is turned off while installing rock wool and ceramic logs in a gas fireplace.