Start by painting the tiles with chalkboard paint on both sides. One tile I painted pink and put a little bubble on.
Once they're dry, hot glue the jewelry thingies on them. I'm not sure what they are called, but you can see them in the picture.
Then just hang them on a necklace or string. I got some cool little rubber necklaces for mine at the craft store. You can add some beads or just leave them as is. Best thing... you can change what's on the necklace whenever you want!