Move the wire racks of a kitchen oven to allow yourself room. Preheat an oven to 400 degree (F). Hold the wire end (just off the head shrink) with a pair of tongs.
Open the oven door. (careful, there will be a blast of hot air) Insert the tongs holding the wire. Do not allow the wire to touch anything. The heatshrink should do its thing within 3-10 seconds. Remove from oven as soon as the shrink has shrunk.
Good luck.
P.S. You could also use a heat gun, available at Sears or Home D.