The very first thing you have to do is grab a clean empty spray bottle and fill it with some bleach.
Now, place your dark cotton dress on a smooth surface and remove all its wrinkles with the help of your hands. Now, deliberately spray the bleach all over your selected cotton dress.
Note: While applying the bleach, make sure to wait for it to start working before you splatter more bleach.
Set the bleach applied dress in the sunlight until dry thoroughly. Put the dress through the washer and place in the sunlight again until dried completely.
Take a bottle of soft fabric paint and lightly spray the edges of the bleached galaxy print on your dress in order to give it some depth. You can get a clear idea of this activity from the image on your right hand side. Once you apply fabric paint, set your dress in sunlight for a few more minutes until dried thoroughly.