Generally, you need to release the halyard tha t holds the sail up on the furler. On some furlers, you have an external halyard (you should be able to see it attached to the top of the Genoa, to the mast. Location on the mast depends on if you have a mast head rig, or a fractional rig.
On other furlers, like mine, the sail is held in place by a wire halyard in the furler. On mine, I have a metal "slug" that is attached to one end of the wire halyard, and as I raise the sail, I pull down the slug. Once the sail is in place, the slug is "pinned" in place with a cotter pin. The slug is pinned a foot or so from the bottom of the furler.
Knowing what sort of furler you have would help immensely. But these the options should give you some good clues where to start.
Greg