If yours is wood burning get in touch with the manufacturer and see if it can be done. You can also check out a good fireplace store and thay may be able to assist you. BTW...this is not a DIY. You would need a plumber to run the gas line. There may also be codes that need to be followed.
Hi Allan - here are some videos that can help you:
Could be worth a few hundred dollars to have a pro do this.
I agree with Mogie, installing a gas anything could void your homeowners insurance if you have a fire or explosion.