This is one of the hardest things to do, so don’t get frustrated if you can’t do it perfectly. The best place to do this is on a flat surface. You lie the sheet out so that the elastic is facing you. Then, you pick it up and make sure it’s straight and all of that. It begins with a simple fold in half. Easy enough, as long as you make sure to tuck the corners in. This’ll help keep that fluffiness that makes this hard to do in line.
Then fold it again in half, this time widthwise. Flip and repeat. Now, your sheet should be as long as the bed, but very narrow comparatively. Fold in half lengthwise, and then fold it into thirds. Voila!