I bought all my stuff from Ecuador, but you can also find these things at Michael's.
1
These are not my instructions, but follow the steps. Keep on going until it fits right on your neck.
2
Add your stone when your done. I use a seed called taghua. I doubt you can find it hear, but you can try something else you might like.
Cut a small piece of hemp and attach your stone to the necklace. Your done:D