It's real easy. Just cut the heads off the old rivets with wire cutters, and push the remaining piece out of the hole. Or use a drill or dremmel tool to drill or grind off the head. 1/8" drill bit. Once the old rivets are out, simply insert the new rivet into the rivet gun, line up the flap with the hole, push the rivet in and squeeze the tool to close the rivet. Once it closes completely, the protruding "nail" breaks off. Shouldn't take more than a few minutes.