The skirt attachment can be a little "fiddly" as some have said. There are pockets under the pocket flap right at the back seam of skirt to center back pieces.
The image on the left shows the pocket flap and one pocket edge sewn to the skirt. The right hand image shows the same but without seeing the flap. You can also see the center back part of the skirt which is cut in one long piece from the upper back.
The other edge of the pocket will be attached to that center back piece, but not the at the center back seam.
The directions are fairly clear and pretty well illustrated. I always lay it out on the ironing board and pin it together to make sure I am doing it correctly. To the right you can see the pocket right sides are folded together, the flap is laying on the center back piece, the seam is lining up with the side back seam and it is ready to stitch to the body pieces.
With both skirts attatched and pockets accessible under the flaps, we are ready to move on. There will be large Navy buttons sewn at the top of the flaps (side back seams), one at each side. There will also be medium buttons sewn on the flaps themselves.