Using the CND Plexigel Builder is easy. First, make sure your nails are clean and dry. You can apply it directly on your natural nails or over a tip or sculpting form if you want a specific length. For cracked nails, use the wearable patches to fill them before applying the gel. If your nails are broken, repair them first and then add the gel. To shape flat nails, apply the gel and mold it to get a plump look. When building the length, layer the gel as needed. Remember to cure the gel as per the instructions. As for maintenance, avoid using your nails as tools to prevent breakage. Keep your hands clean and moisturized. If you notice any lifting or damage, it's best to visit a professional nail technician for repairs.