Prepare your room for painting by removing any furniture and placing tarps over the floor. You may wish to use a small stepladder to allow you to get closer to the ceiling. If you're going for a more dramatic visual, you may wish to paint your ceiling black before proceeding with the stars. The glow paint is effective, however, with any colored ceiling.
Place the stencil over the area of ceiling where you wish to place a constellation or zodiac and use your small paintbrush to dab points of a glow paint into the holes of the stencil. When you're finished, remove the stencil.
Add additional stars by dabbing small points of paint in locations that you wish to place stars.