Here's a video on how to remove the top plate of a FTN:
If you don't have a optical spanner like in the video, you can use a rubber glove or something "grippy" to use friction to remove the screw.
Just be sure to unscrew it in the proper direction!
On page 17 (marked page 15 at the bottom of the page of the document) of the following file, the winding-knob cap is marked as item 402. Nikon labels this “Take-up lever retaining screw” in the parts list.
The note indicates that this part can be gripped with a sheet of rubber (to increase friction for gripping). It appears to have a small-diameter screw shaft underneath. I think it simply unscrews from the tapped hole in the upper end of the winding shaft (part 430 of the PDF page 19 or page 17 as printed at the bottom of the document). This part is labeled “Take-up shaft” in the parts list.
The top end of the winding shaft is the small shaft with the diametrically-opposite drive flats. This is seen at the center of the circled part of the photo shown in Post #1.