Place one foot in the middle of the BOSU . You may want to start by holding onto something or hand against a wall. Stand up on the BOSU and place one foot on the back to get your balance, and then slowly let go of your support and raise your foot. The aim is to keep your balance and to try and stop the BOSU from wobbling excessively.
If you are new to using a BOSU it is normal to wobble or shake when trying to do these exercises at the start. As you get used to the exercises and your body learns to control the movement this will stop.