2013 Denali, how do I enable the RSE into the Nav unit?

[pendragon]

My 2013 came with the factory Nav unit but without the RSE, I wanted to add the audio and video inputs to my truck, United Radio made me up a cable that fits into X3 on the back of the Navigation unit, but what do I need to do to tell the Nav unit that I now have an RSE?

United Radio did say thatt he Nav may need to be re programmed, is this complicated?