Stand side on to BOSU with feet facing forwards, hip width apart, knees slightly bent. Aim to step not onto the top of the BOSU and not onto the side but about 3/4 up to the top. Bend your knees and step sideways onto the BOSU, ensuring you keep glute and thigh muscles switched on so your knee does not fall inwards and keeping ankle steady. Step up the other leg and straighten up so you are standing - but don't let your knee roll inwards. Reverse the process to step down like you would in a squat.