Where do you plug the ground antenna wire into?

 

On a 1996 XJS

 

There should be a small port near the aerial mast to plug into. I believe you have a German made Hirschmann Antenna motor unit, but the Japanese made ones are similar.

 

It’s not the end towards the rear of the car it’s the end in the front I’ve been told it plugs into the back of the radio but I don’t want to take the whole radio out if I don’t have to.

 

Any wire at the back of the radio, power, ground, and antenna are only accessible by taking out the radio. I believe that the oem radio had a harness of these wires, as well as speaker connections. If you're uncertain or intimidated by removing the radio from the dashboard, any competent audio technician can easily do it.