Open both of the bifold doors all the way. Press on the top of the first door until it pops out of the track, then lift the door out of the bottom pivot.
Push the top of the second door out of the top track. Pull the door up and out of the bottom pivot.
Use a Phillips-head screwdriver to remove the screws holding the top track or clips in place. Pull the track away from the fireplace. Remove the screws that hold the bottom track in place and pull it away as well.