I don't have a mandrel here at home, so no photo, but it is a tapered rod with lines and numbers corresponding to ring sizes. After you string the bead or beads on the wire, you center them and hold the bead over the correct size on the mandrel and then begin the wrapping process, bringing one end of the wire up one way, and the other end up around the other side of the bead. You finish it off by sliding the ring off the mandrel and wrapping the wire tightly a few times on either side of the bead to hold everything in place.
Very hard to describe in words, and I'm sure there's a video tutorial somewhere here in cyberland. I did one with silver wire, one with gold, and one with a gorgeous chocolate brown wire.
Is this too much?