This is similar to one of the hamstrings stretches: Lie down. Stretch your right leg over your head and then to your left shoulder. Breathe. Hold down the leg with your hand, moving it closer to you each time you exhale until you cannot bring it closer to you. Hold for 10 seconds. Repeat with the other leg. Hold for 10 seconds.
Alternatively: Lie down and bend your left knee. Place your right bent leg in front of your left leg so that the middle of your right calf is over your left knee. Now bring your left leg toward you. This stretches your right gluteus maximus muscle. Bring the left leg toward you until you cannot any more. Hold for 10 seconds. Do the same for your left gluteus maximus.
Disclaimer: None of the above information can be taken as a substitute for advice from a medical professional such as a physician.
My third book, Pocket Guide to Fitness, is available on www.louizapatsis.com, http://www.authorhouse.com, www.bn.com and http://www.amazon.com. If you look up my name on those Web sites, you will find my other books The Boy in a Wheelchair and Life, Work and Play: Poems and Short Stories.