To use this Royal Canin canned cat food, simply open the can and serve it to your cat. You can feed it directly or mix it with your cat's regular dry food. As for the amount, it depends on your cat's age, weight, and activity level. Usually, you can follow the feeding guidelines on the package. Keep in mind that this product is going through a packaging change, so don't be surprised if you receive different packaging. Store the opened can in the fridge and use it within a day or two. And always make sure your cat has access to fresh water.