Take your phone out of its case.
Find the mute button opening on the phone case. (if you don't have one on your case, you can use a different side opening.)
Insert the looped end of the phone charm through the mute button opening. Do not pull the gemstones through the hole.
Tie a knot by using the looped end. Open the loop with one hand and pass the beaded part of the charm through to form a (lark's head) knot.