Guided imagery isn't the screen of your car's GPS. It's actually a way of making you feel better. The technique has been shown to improve the ability to cope with depression, improve mood and decrease stress.
How do you do it? First, go to a quiet place. The bathroom often works well, since privacy is usually respected there. Start by relaxing and breathing deeply, then visualize yourself in different scenarios. Some variations include visualizing yourself in a pleasant place (the beach), fighting disease (seeing your good immune cells fighting off bad germs) or practicing for a big performance (doing well in your job).
How can this cure aches and pains? If you're in pain, visualize the spot of pain. Follow the nerve from that spot to the center of your mind. Ask your body if you can take control of that pain, and visualize the way that would happen.