You can make the conversion by simply adding a gas log set or by installing a self contained gas insert unit with its own chimney.
Converting wood fireplace to gas insert.
Licensed gas plumbers and contractors typically do the installation for gas inserts and log sets.
Options usually depend on the type of fireplace.
Because the existing chimney liner used by the wood fireplace is designed to burn only firewood a gas fireplace insert would require the installation of a collinear gas insert liner in the fireplace flue to the chimney top.
These include converting the unit to use gas logs using a gas fireplace insert which also makes the fireplace much more efficient or converting the fireplace to a vent free appliance.
A wood burning prefabricated fireplace will need a conversion kit but masonry fireplaces have several options.