Fill a cup with a dirty pour. The more colors you have, the darker it will be.
Pour one color on the top half of the canvas, be sure it goes over the edges. experiment with putting the color on the entire thing.
Ribbon pour it starting near the edge of the purple, and at what place, is up to you. Near the top, at the middle or the bottom only. Each gives you a different look and it is personal preference.
Move the paint around as much as you want.