Look at the handle very closely,on the round portion-you should see a tiny
spot of a sealing compound,which you need to dig out VERY CAREFULLY.Then you
will need a tiny flat-bladed screwdriver(like a jeweler's type)to unscrew a
tiny locking screw  that holds the cylinder in place.Remove the lock cylinder
with the key installed to minimize the chance of losing all the tiny cylinder
pieces.Good Luck!

Karl