Cold, the harness is actually labeled on what does what. The only two wires you need to be concerned about are the B+ and E. B+ needs to go to the relay and earth is ground. Both need thicker gauge wire. Personally, I would take the pins out of the harness and solder new thicker gauge wire directly onto the pins. I hope this diagram of the Relay helps. The 12V fan wire should go to the B+ on the FPC.
http://www.titantalk.com/forums/attachments/titan-general-discussion/78244d1240275985-looking-10-amps-under-hood-relaywiring.jpg