Let's see. I do not know what path you follow, or what God(s) Or Goddess(es) you follow, or what tradition or path of magic you follow.
What I would do is place the coin in your hands, and verbally pray over it. Asking for it to be charged with whatever energy you want. You can also say a prayer to your Higher Power, asking them to bless it.
For me, I like to give my coins that I will be offering up and using in workings a nice bath in some Holy water. If I have Florida water on hand I'll pour a touch of that on them as well to cleanse them. As I do that, I will pray over them a couple times, and ask that they be cleansed and blessed. That is just my way of blessing my coins.