2006 Ford 350 PU wiring question

[Stumped]

Trying to hook up an accessory to the one of the four factory installed accessory switches on the dash board but can't find the wires, fuse location etc.
Stumped!
PLEASE HELP!!!!
Any Ford mechanics in or near Concord, NH?
2006 F-350 Diesel.

[l3ond]

Probably a little late, but I thought I would answer this for anyone else that finds this post. The brake controller relays and accessory switch fuse box is behind the glove box above the left-hand side where the notch is in the glove box. It has a label on it with very large writing that says ACCESSORY FUSE PANEL, with a diagram of what each thing is. The wiring to hook something up to one of the four accessory switches is located in the engine bay, right on the firewall of the driver's side. I can only say for sure that this applies to the F-250's and F-350's from 2002 to 2006.