Place the band above your knees.
Lie on your side, with your head resting on your bottom hand. Elevate your feet to hip height (if you can), keeping your knees touching the floor.
Keep your feet together as you lift your top knee toward the ceiling.
Slowly lower the top knee down to hover right above the bottom knee. That's 1 rep.
Do 20 reps. Switch sides and repeat.
If it's too difficult to open up your knees with your feet in the air, leave them on the ground and do the same movement.