If you do it like
http://syty.huryde.com/html/tech/starter.htm shows, you're splicing the Ford solenoid into the main hot wire to the starter. Instead of being hot all the time, it's now switched. So you bridge the "hot" terminal of the starter to the "switch" terminal of the starter solenoid.
Note that someone recommended NOT doing it this way. The "starter click" problem doesn't have anything to do with the main power wire to the starter, so why mess with it? Putting the solenoid in and using that wire to also trigger the starter solenoid can put more load on it, leading to the starter motor having less power to turn.
The solenoid circuit is the one that has problems, so a Hot Shot-style relay should take care of your problems. Use the existing purple wire (the one going to the solenoid's "switch" terminal) to trigger a relay, which feeds power from a hot source (the main starter wire, the battery, etc.) to the starter solenoid's "switch" terminal (where the purple wire used to go). In our case, I'd feed the relay from the battery or something. The Hot Shot instructions say to use the hot terminal on the starter, but all the heat down there is one of the main causes of all our starter problems...
