Sorry, my repair manual stops at 2005 (good enough for the '94 and '98 though). So, invest in either a generic Haynes or Chilton or get the official Ford 2006 volume set and especially the electrical diagram. Sometimes the Vaccuum and Wiring Troubleshooting book is enough once you figure out how it works.
If the fuse box is still in the dash driver's side in '06 then one option would be an unused fuse slot which only receives 12v when the ignition is on but zero when off. You'll need the battery connected to test, of course, but I recommend disconnecting the ground off the battery during installation of the power wire. If not specified in your instructions, try a 5amp fuse at most of the correct type (blade). I would not tie it into another circuit, especially not the ECU, security module, or air bags. Perhaps the radio.