"Dear everyone. This is literally the exact opposite of moonwalking. STOP DOING IT!" As you can see, he's doing thing where the person basically just walks backwards in a really awkward fashion.
"Slide on your goddamn heel!" Here, you can see that he's putting all of his weight onto the balls of his left foot while he simultaneously drags his right foot backwards. Note that his right foot does not lift up off the floor.
"Shift all of your weight onto the other foot." Basically, he flattens his left foot before shifting all of his weight onto the balls of his right foot.
"Now slide your other foot backwards, on the heel." The practise is in trying to effortlessly shift the weight between your two feet.
"The strides are good. Nice and long." i.e. Try to slide back as far as you can before shifting your weight over onto the other foot.
Here's what your moonwalk should look life after some good old fashioned practise.