The process of receiving the right to give Reiki services is known as a Reiki attunement. A Reiki Master teaches a Reiki workshop.
administers the attunement and uses one or more breathing exercises to touch the student's head, shoulders, and hands. The Reiki Master then channels the attunement energies to the student.
Attunement energies are unique energies that follow the Higher Power's guidance. These energies often change as they pass through the student's energy channels, binding him or her to the Reiki source.
The energetic component, which is directed by the Higher Power, changes itself during the attunement to become exactly what the student requires. During the attunement, some students can see divine beings or see colors. Others can experience a warm sensation in their hands. Students undergoing attunement, on the other hand, may simply feel more comfortable without having an inner experience. An attunement is effective in both cases.
You may also want to read more about Reiki Healing here.