Placing the hands on the bench is one way to pivot when playing pedal exercises or solos (imitate the video example or follow these steps):
Begin with your body centered on pedal D and your feet placed on the surrounding keys C-sharp and D-sharp. Place your hands to your sides palms down on the bench, curling your fingers around the front edge. Now using your hands for leverage, pivot on the bench so that your feet reach the lowest C-sharp and D-sharp. Play those two keys alternately with the toes.
Now grasp the key cheeks on both sides of the lowest manual instead of using the hands on the bench for leverage. This is another way of pivoting (imitate the video example).