Relay harness for towing

Installed a reciever hitch and t connector for lights. Tail lights did not work, had to purchase a relay harness from Nissan. Didnt come with instructions, of course. This is a 2007 model 4x4. Where does this Relay harness go? Thanks!

the harness if its part number starts with 26 it's the trailer brake harness???

goes under the dash

The part number is 999T8-KR010.
I installed a light connector to the rear trailer light plug underneath the drivers rear side. All lights work except the tail lights. Instruction on connector stated on model without the factory tow package would require a relay harness available from nissan dealer for the tail light function to work.
Purchased one from Nissan. No instructions included. An online site of www.Nissan-Techinfo.com was included with kit to obtain instalation instructions. However that site only help to give info. on srrius or a satelit radio instalation. No help. Just need to know which area i need to start looking for the harness to go.
Thanks

Here is the update in case anyone else tries to wire their vehicle for a trailer.
You need to purchase the realy harness from Nissan. cost $80.00.
The harness has 3 relays on it and it connects under the passenger kick panel. It plugs right into the open receptacle. Their are 2 that look the same. It plugs into the shorter one that is tucked behind the main harness that you will see.
This is needed and the only way to have tail lights work for trailer. Hope this helps someone!

That helped alot, thanks

Went to the dealer and got the same terrible "instructions" in the package. Finally found this video from eTrailers which really details what you're supposed to do - http://www.youtube.com/watch?v=o5FkSILF7jU

Now how do i mount this damn 7-pin to the hitch receiver? Oh wait. It's already a topic: http://www.clubxterra.org/forums/showthread.php?t=4262

Thanks guys. You're more useful than someone who actually works for Nissan.