The top frame must of course be in good condition and mounted on the car prior to starting this installation. The wooden header rail attached to the front bow of the top frame must be complete and in good enough condition to hold staples or tacks. If your car has been kept out doors for some years, chances are that the header rail may be badly deteriorated and need replacing. I had replaced mine some years earlier, and the car has been garaged most of the time when not in use, so my header rail was still in good condition and would be reused. When I did replace that header rail, as I recall there was some minor wood work required to fit it to the top frame. I'm sure it depends on the source of the rail, but the fitting was fairly straight forward at the time.
The header rail is fastened to the top frame with wood screws and has a metal bushing and a thumb screw at each end. At some point one of the female threads for this thumb screw stripped out. The thread is 5/16" diameter but has a strange pitch that is no longer standard, so you may have trouble finding a Heli-Coil to fit or otherwise repairing it. My solution at the time was to drill it out a tad larger and tap it for a 3/8" fine thread. I then used a 3/8" fine thread hex head bolt and welded a short piece of 1/4" round rod across the top for a wing head.