I found this cool Marcasite buckle from the 1920's at a flea market. This was a true find. They are difficult and rare in a bargain box, and I swooped on it Many times I will stack various findings on top and glue them down with E6000, then attach them to the buckle after I have made the bead chain and clasp.
First, you need some handy dandy bending pliers. I got them from Gilding the Lily. You squeeze the buckle in this tool a little bit at a time to create a bend the will fit naturally over the wrist. Test it on your own wrist to make sure the curve is right.
Next, make your bead chain. I find if I use strong steel pins, I don't need to wire wrap them. If they are special beads, by all means, wire wrap them on to insure they will stay on.
Look at the bracelet for a good space to connect the bead chain. If there is no space, you can make one with the riveting tool (also available at Gilding the Lily) or with a fine drill bit. Sometimes you need to use a jump ring in the bracelet, and then attach the bead chain from there.
Create your focal assemblage with lace and broken jewelry parts. I layered them all together into a pleasing configuration, and then glued it together. Let it dry overnight, then glue the focal as one piece onto the buckle base in the desired position. .
Measure your wrist, and make sure the bead chain is long enough to fit properly. Add a clasp. Now you have a lovely bracelet made from a buckle that is trendy and fashion forward.