I have a Debbie Bliss book with a hooded sweater in it but I don't know if it's the same type.
Do the finishing directions say "Fold cast-off edge of hood in half and join seam. Sew cast-on sts of hood to bound-off edge of back neck?"
If it does, you just bring the edges you bound off for the hood together and sew them so they'll be a seam across the top of the head. Then sew the back of the neck stitches together with the bottom of the hood stitches at the neck.