Doing the duck run / walk is simple. Think of a duck when they walk — they have a sort of waddle.
So, to start, turn your feet sideways with your toes pointing out. Now step over your skates while driving your knee forward. Bring one leg in front of the other. Be sure to set your foot down with your toes pointing out to the side. Do this slowly at first and gradually work up to trying running as shown in the video below.