Case/back of phone must be clean prior to adhesion.
Remove backing from 3M sticky tape on phone jewel.
Press phone jewel onto back of phone in location of your choosing.
If the phone jewel ever becomes unattached, it CAN be reattached!
To reattach, make sure to wipe case/back of phone to ensure cleanliness - wipe with damp cloth on sticky tab to remove any debris that might have attached, after dampness dries from sticky tab, reattach by sticking back onto case/back of phone.
This process can be repeated as needed. Though the life of your phone jewel and its stickiness should last quite a while!