Use a stool/stepper of appropriate height
You can choose the height of the stepper based your comfort levels
Start at the top with both the feet in line with each other
With your eyes looking straight ahead, take a big breath and extend right leg back to perform a step down
Land softly on the ground and push yourself up with the heel of your left leg
As you go up, push the right leg to the chest to perform a high knee
Hold the top position for a second
Get back to the starting position and repeat the movement