you take a bolt that is the same thread pattern as the inside of the insert. Cut off the bolt head so it's just threaded rod, and screw on two hex nuts about half way up your rod. Tighten the rod in your chuck, then thread on the insert so that the end of the rod is just coming out of the bottom of the insert. Spin your nuts down the rod until the bottom makes contact with the top of the insert. Place your tap, upside down, on your drill press table and line it up with the insert (hole already drilled out of course). Lock the quill in place so that it is making steady pressure with the tap. Using a wrench, tighten the top nut until it drives the insert into the handle.
Re-reading that, well let's just say if your mind is normally in the gutter, you'd have a field day with that description.