Lie down and keep your back flat on the floor, as much as you can because everyone is built differently. Keep your arms to your side unless you need to hold onto something heavy for support. Raise your legs straight, toes pointed, half a foot from the floor If this is too low, they can be as high as two feet above the floor. Higher is easier. Open and close your legs like a scissor. For added difficulty, move one leg at a time to your side. You only need to move your legs about 45 degrees to each side (angle between your centerline and leg). Do four sets of ten repetitions. You can do the same exercise lying on your belly.
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.