Using the Paw-Ready Bite Block is super easy. First, put your finger into the block. Then, gently insert it into your pet's mouth and start brushing their teeth. Remember, go slow at first so your pet can get used to it. As for the size, pick the small one if your pet weighs 5 - 15 lbs or is a puppy with 28 baby teeth. Choose the medium one if your pet weighs 15 - 85 lbs. When it comes to maintenance, after each use, just rinse the block with warm water and let it dry. This will keep it clean and ready for the next brushing session. And always store it in a dry place.