I don't have actually origami paper, so I am just using plan college rule notebook paper.
You want your paper to be in a square. To make a notebook piece of paper to be a square, take a corner and fold it downward to make a big triangle.
Cut the rectangle piece off.
For this project leave the piece of paper in the triangle. If you have paper that is already a square, take one corner and fold it diagonally.
This is how it should look after that
Flip item over
Take the flaps and fold them downward to look like picture