Here's how to do it: Stand with your feet hip-width apart and toes forward. Lower into a half squat, making sure your knees don't extend past your toes. Raise your right knee to hip level and extend it out to the side with your foot flexed. As you kick your right heel out, you're also going to straighten your standing leg. Pull in your right knee and return to the starting half squat position.
Do 10 reps on your right leg, then repeat on the other side.
Try this move: Squat With Side Kick