I am often told "I don't know how to meditate. I just can't quite my mind.". My response is always, it's normal to feel stressed and unable to sit quietly. Which is why I often recommend other forms of meditating, like walking.
Walking is another way to meditate for people who can't sit. It brings one to the point of realizing that the benefit of meditation does not depend upon the position of the body. Sitting, standing, lying down, walking — what is the difference when one is aware? The state of being aware is an experience which goes beyond the body. Not only are you aware of your movements, you are also getting exercise.