Maybe a little more in depth answer since we don't know how mechanically inclined you are. When you cut the zip tie that is on the boot, the plug wire will pull out of the boot with some force. It won't look like a normal wire that you strip off some sheathing to use crimp on style connectors.
The spark plug wire and sheath will be even on the end. Then depending on how much length you can spare, trim off 1/8-1/4 of an inch. This will give you fresh clean wire ends, which will still be flush as you cut through the entire cable. Slide the cable back into the boot, which has a metal spike that will be forced into the plug wire creating the connection. Just make sure you slide it in as far as you can, and replace the zip tie that was on the boot originally.
http://www.youtube.com/watch?v=nyi_77uAij0&feature=youtube_gdata_player