how do I access the bolts on driver side top hinge on 93 XJS?

Door hinge I assume (and not trunk/hood)? May need to remove a fender to access all door hinge bolts. It's like that for a lot of cars/trucks.

Assume your talking about the Driver's Door. See my Answer below for a "source" to get the replacement Hinges for my 1996 XJS. I had to remove the entire Driver's Door and the lower firewall near the driver's left leg to change out the Hinges. I changed the upper and lower Hinges at the same time. Door realignment (same size clearance opening all around door perimeter) with the new Hinges is definitely a 2 man job and challenging. May or may not require proper Door Hinge Shims. Best to lubricate the new Hinge Pins before installing Hinges. Very difficult to get lubrication in to the Pin after install.

An addendum to my previous comment. I did have the Dash Board "loose" and brought back some at the time and I don't really recall if this was necessary for access to the upper Door Hinge Bolts. I also needed access behind the Dashboard at that same time for changing out a portion the Passenger Side Dashboard Section for the Air Bag which is bolted in from the backside. Access to the passenger Side Air Bag area looks like an "afterthought". Only access to these bolts is to remove the entire Dashboard and pull it out about 4" to 5". Same for changing out the Air Bag.