Just take a razor blade or exacto knife and strip the plastic back a little bit all the way around the wire. Once the wire is exposed pull it apart in the middle and then push you second wire throught the "hole" that you made and wrap the excess around the rest of the wire. Lay the two wires together and tape it back up. Good to go. If you want to make it even more secure then solder the wires together before you tape it back up.

Axle