Spread a tarp across the room, put on goggles and connect the extender rod to the roller brush.
Open, mix and pour the primer into a paint tray. Push the roller brush into the paint over and over again until the brush is covered in paint. The brush should not be dripping with paint.
Roll the brush over the water spots on the ceiling. You will need to prime the entire ceiling to help ensure an even finish. Allow the ceiling to dry. Repeat with a second coat of primer if you can still see the ceiling spots.
Open, mix and pour the ceiling paint into a new paint tray. Roll the paint on the roller brush. Paint the entire ceiling. Allow the paint to dry.