Caverboo, the wiring harness you will need to access is in the tail of the ST, unfortunately their is no plug & play option and you will need to splice in.....
If you are at all concerned about your ability to locate, splice, solder the trailer wire into the ST.....just run the trailer wire from ther plug wired as per Allans diagram into the tail and have a local Auto Elec complete......it would honestly take them well less than an hour to complete properly.
cheers