Remove any cracked or damaged sections of the area you need to repair. Put on work gloves, safety goggles and a dust mask, then use the edge of the flat metal trowel like a floor scraper to pop up or scrape away any loose segments. Sweep the area, vacuum it and clean it with a damp rag. Allow the surface to dry completely.
Mix up some of the self-leveling cement compound in a bucket with a low-speed drill and paddle. Add enough water to create a smooth, creamy mixture that is just on the runny side, with the consistency of thick yogurt. Let it sit for a few minutes after you have mixed it initially, then mix it one more time.
Pour the self-leveling mixture into the patch area where you need to repair. Smooth it over with the flat metal trowel. Move the material over the repair area from different directions with the trowel to ensure it is bonding with all sides of the patch area. Let it dry for 72 hours before allowing foot traffic.