Check out this site for more information on mindfulness:
There is a great learning section on this site with tons of relaxation/mindfulness activities for any age.
Activity 1: Stop, Breathe, Think
1. Review: The Basics of Mindfulness activities (If it's your first time)
2. Pick out a breathing activity to do-(under list of activities) I suggest starting with the first one, "mindful breathing", for your first time.
3. Get comfortable and relax!