To put together the book after you've printed it out (diagrams here):
- Fold in half and crease, with the text facing out, along the registration marks, both the long and wide way. Since every printer is different, you may have to trim a bit of the margins to even up these edges.
- Open it out, and then fold each side in to meet in the center (again following the registration marks).
- Slit the paper along the tops of the center two sets of pages, then pull open this slit at the folds. Fold book so that the covers are in front and back.