What is the wire for and where does it plug in?

[bighause]

I added everything for cruise control in my 89 MJ from an 89 XJ and it is not working. I think this wire is my problem, but I'm not sure where it plugs into.

 

This is not my picture but the plug on the end of the wire is loose under my dash

 

[Boots]

I think that mine might have plugged into the yellow box under the dash. I could be wrong though.