Fold the page in half vertically
Fold the page in half horizontally
Open the page flat, fold the left side inwards to meet the central crease
Now fold the right side of the page to meet the central crease
This should leave the page folded into eight section, Cut a slit along the main vertical fold the length of the two middle boxes.
Fold the page in half vertically and push the two middle section, where the page has been cut, outwards.
Now fold all of the section into on booklet, creating a front and back cover.