Paint a concrete floor by cleaning the surface, applying the paint and applying a sealer. Select a paint that the manufacturer rates for use on concrete, and use a long-handled roller for easier application.
Before applying paint, remove any dirt, oil or debris that might mix with the paint or keep it from adhering to the surface. Wet the concrete with water from a garden hose, and apply a mild detergent solution with a broom or long-handled brush. If the patio is heavily soiled, mix trisodium phosphate with water, and scrub the surface. Rinse with clear water, and allow the surface to dry before proceeding.
Immediately before applying the paint, use a shop vacuum or broom to remove any dust or dirt that blows onto the concrete while it dries. Mix the paint, and pour it into a tray. Follow the label directions, and apply two or more coats for best results. A second coat makes the paint stronger and more resistant to chipping.
Wait until the paint completely dries before proceeding. If the plans include creating a pattern or outline with a different color, waiting ensures the colors do not blend. After applying all coats of paint, wait for the complete drying time again.
Sweep the dry surface before applying the sealer. Use a clean paint pan and a new roller cover to apply the sealer in thin coats. Apply as many thin coats as possible for a long-lasting finish.