on the 2004 F-150 i had, all you had to do was pop the switch out. On the back of the switch you took the wife for the fog lights, and tapped the wire for the running lights into it. this turns your fog lights on, whenever your running lights are on. It does this by sending voltage to the relay for the fog lights. ITs pretty simple to do. here is a pic of my lightning's switch.
you can see i just took a scotch connector and jumpered the wires
if anyone has the schematics for the switch it would be easy.
another thing to do is pull the switch and measure voltage on the wires in different switch settings
