Scrape over the damaged area with your drywall knife, removing any loose plaster or paint.
Spread Spackle over the inside of the exposed area in a thin layer so the area of missing plaster is still indented.
Tear and set strips of paper drywall tape into the damaged area, putting them side by side in the Spackle. Make sure the whole area within the damaged section is covered.
Let the Spackle set for an hour.
Spread more Spackle over the damaged area about ½-inch thick. Let it set for four hours.
Spread on a third coat of Spackle, getting the damage area level with the surrounding plaster. Let it set for six to eight hours.
Sand the area smooth with your drywall sanders. The ceiling is now ready to repaint.