Grab a bar that gives you a good workout and is doable for four sets of the repetitions. Do five if you are a man. This is a difficult exercise. Assume a push up position. Place the bar on the center of the Bosu Ball. Do your push ups. You will be using up lots of balance and strength just to stay on the Bosu Ball. If you are a beginner, you may only be able to do one or a few repetitions. That is fine. Go at your own pace.
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.