Mop the floor with a degreasing solution, and rinse it with water. Allow the floor to dry. Sand away any previous paint, and vacuum the floor.
If needed, use a trowel to fill the cracks and holes with concrete patch compound, and let the compound dry.
Apply a coat of primer with a paint roller, and let it dry. Apply the second coat, and let it dry again. With a paint roller, apply the first coat of paint, and let the floor dry. Apply subsequent coats as needed, letting the paint dry between the coats. Finally, apply coats of masonry sealer the same way as the paint, and let the floor dry.