It is easy. Think about what you want it to do and write a basic spell for it. I did this with my class ring and since it is something special to me the enchantments are stronger hope this helps. dark blessings
You can bless it with each element. Run it through smoke saying "may the spirit of air bless this and keep the wearer from harm", pass it above fire, sprinkle water over it and then an herb mix for blessing (to represent earth). Each time exchange the word "air" for the proper element you're using.
There are a million ways to bless. It all depends on what type of energy you want the amulet to have.
With a spell. Hold the amulet in your hands. Picture in your head what it is you want the amulet to accomplish in full detail. Chant the following, once you can clearly visualize what it is you want: " I give you joy and breath and life I give you purpose, plan, and sight do now what I ask of thee as I will, so mote it be.