The stones can be used in a variety of different ways. The best way is what is comfortable to you, because constant contact is the best way to have an effective reaction with the stones.
When using Stones, mud packs, or water stones, the purpose is to get low dose radiation to the affected area.. These are such low levels that they have never been proven to be harmful! The radiation is not attacking the problem, it is assisting your own body systems to respond.