To litter train a cat, start by placing the litter box in a quiet and accessible location. Use unscented, clumping litter as most cats prefer it. Show your cat the litter box and gently place them inside it after meals or naps. Reward your cat with treats or praise when they use the litter box correctly. Keep the litter box clean by scooping it daily and changing the litter regularly. Be patient and consistent with the training process to help your cat learn to use the litter box effectively.