Hi,
Mollie used an awl to punch holes in the leather for stitchin, then she used a needle to stitch the charm in place, and hid the knots behind the charm. She also stitched the attachment ring in place. (Altogether it was basically like sewing a button back onto a jacket, except she had to punch the holes first.)
There are a few other tips on the bottom half of this page in our design gallery:
http://www.rings-things.com/gallery/displayimage-1369.htmland I'm happy to answer anything else I can help with, too!