The instructions give height and width that you are supposed to cut the paper decal that should have come with the kit - typically found on the same small sheet as the Japanese flag. In many older Japanese 1:700 kits, these are just printed on paper, and have no adhesive or decal film. These paper decals should not be soaked, and are best mounted with thinned white glue (Elmer's) or canopy glue if you have some of that on the hobby bench.
I've never seen any build (other than some early builds of my own) actually use those decals, although the pagodas look very barren in the early Waterline kits (1970s) without such bridge detail.
More recent releases of IJN battleships include transparent "glass" bridges. And lots of builders use photoetch bridge windows, painting behind or carving out and then overlaying the PE. Lionroar makes a PE fret with several styles of IJN bridge windows.
Group Build (Shiver Me Timbers):
1:200 Trumpeter Arizona, 0% complete
1:700 3 Flight Deck Akagi, 10% complete