For each page you'll need a sheet of paper the same size as the paper you used for your box, a photo or piece of card 7.5cms sqr for 6*6 papers, 10cms sqr for 8*8 paper as well as 1 less piece if card 5cms sqr or 7cms square for the hinges. I made 6 pages so only needed 5 hinges. If each page is going to be heavily embellished or you use a thick paper 6 would be the maximum pages that would fit the smaller box. Thin paper with photos and rubdowns you would probably get about 10 pages and you can fit more pages if using 8*8 papers.
Start off by bringing the sides into the middle and folding, unfold, turn and repeat. If you have difficulty finding the centre line you can fold the paper in half first either across or diagonally but this will leave you with extra creases showing on the finished frame. I havent worried about it for the step by step but if I was making this as an extra special gift I would probably measure and score the lines with an embossing tool. Ignore all the extra creases on the pic, I'd forgot to photo it so had to go back in at the end, oops.
With the right side showing fold the corner into the middle, repeat for all 4 corners before opening out.