Where is trailer brake connection inside?

Can someone help me find where I plug the factory trailer brake harness inside? I'm setting the Tahoe up to pull our little travel trailer this weekend and I don't know where to plug the wiring harness into.

Thanks Alot...

The brake controller wiring harness jumper plugs into the vehicle relay block-body, which is under the left side of the instrument panel near the left kick panel, behind a plastic cover.