What is a one-sentence summary of the following article?
Paint rollers are soft and rounded so they don’t break apart the textures of the popcorn ceiling. Pick a thick-nap roller, ¾ inches (19 mm) thick or more. Also opt for an extension handle to make cleaning easier. The shape and softness of the roller will protect the popcorn texture from damage. Expose the roller to clean water. Try using a small flow from a faucet to splash or lightly coat the roller. You only need enough to make the roller feel damp. It should not drip at all. Water can easily damage this delicate ceiling, so be cautious or consider hiring a professional. Push the paint roller over the dirty spots. Move in a line, applying an even coat of water. You don’t need to push hard against the ceiling. Rinse the roller when it gets dirty so it doesn’t spread any dust or dirt. Remember to squeeze out the excess moisture before using the roller again. If your ceiling has deeper stains, you’ll need to repeat the process with a cleaning solution. In a bucket of water, add a small amount of vinegar, mild dish or laundry detergent, or bleach. If using bleach, mix 5 parts water with 1 part bleach. If using vinegar or detergent, use equal parts water and vinegar or detergent. Bleach with water works best for smoke, mildew, and water stains. Wait a few hours to see if the solution has had the desired effect on the ceiling. If stains are still visible, repeat the application. You may need to repeat this process a few times for tough stains.

Summary:
Get a paint roller. Dampen the roller. Roll over the surface. Add vinegar, detergent, or bleach. Let the solution sit on the popcorn ceiling and repeat if needed.