The book by the same name is available in most book stores. It is a simple but powerful way of gaining greater control of your mind, body and life. To perform the meditation, you first need to choose a word or phrase that is calming to you. It can be a religious term such as God, Jesus or Shalom or a phrase such as Peace on Earth. It can be a secular term or phrase, as well.
Some people find the words love or peace calming.
The point is that you need to choose something for yourself. Don't pick something that adds to your tension. You can stop the meditation at any time if you feel the experience is becoming too difficult. Preferable with your spine straight. Bring your attention to your breath.