You can practice this outside on a street or flat concrete driveway, or on the carpet in your home. Wherever you want. Stand on your skateboard, with your back foot across the tail of your skateboard. Put your front foot across the nose of your skateboard in the same way.
Now, once you have your feet on the nose and tail of your skateboard, try and and walk. You do this by shifting your weight to one foot, and swinging the other foot forward a little, still on the skateboard. Do this back and forth. Like I said, this might seem a little ridiculous, but relax and have fun with it. It's good practice.
