Reiki in one translation is, “Spiritually-guided life force energy”. I feel intuitively like we used this long ago, and forgot somewhere along the line with the dawn of western medicine. The body knows how to heal itself, it wants to be healthy and whole.
People trained in Reiki receive an attunement, a process where the teacher sends the energy through the students to familiarize the body with the energy. While you do not necessarily need an attunement to use Reiki, it enhances the energy. You will feel more connected with Source energy after your attunement.
If you have not had an attunement, here is how to work with Reiki energy:
Close your eyes. Put your hands out, palms up. Then think of someone you love. The kindest person you know. Think about how that person has influenced your life. Feel the gratitude you have for this person. After a short while, your hands should feel warm and tingly. Put them on your body.
This is Reiki.
The more you work with it, the more you should be able to feel what is happening energetically in your body.