Help with passenger upper cushion seat

How you tighten cable on passenger upper cushion seat! No one can’t seat in the back ,
because the upper cushion seat won’t go forward or bent to get into back seat! How do you tighten that side cable , so the upper cushion seat unhooks and bent forward!

Is it not described in the owners manual? I don’t have an XK8 so no knowledge of the system sorry.

As I understand your situation; the front seat back will not tilt forward because the tab has become detached from the catch at the base of the seat. My first step would be to find an exploded diagram of the seat mechanism. This will help you understand what might be wrong. You could look for one off the internet at one of the Jag parts suppliers. I suspect you will have to remove the back of the seat to access the mechanism.