To shade a cat's eyes, start by lightly shading the entire eye area. Then, use a darker pencil to shade the areas around the eyelids and the pupil. Add some highlights to the pupil to make it look more realistic. When shading, pay attention to the direction of the fur and use short, feathery strokes to create a natural look. Don't be afraid to experiment with different shading techniques to find what works best for you. Remember, shading takes practice, so be patient and keep trying until you achieve the desired effect.