Buying a new puppy is a great fun except for when you have to introduce it to the older family dog. This dog may be resistant to the new puppy and may even be aggressive. Introducing the puppy should be done in a delicate and understanding manner.
Start by understanding the personality of the older dog first and approach the situation with caution based on its friendliness level. Remove all items the adult dog may think of as his. This removes "guarding" tendencies. If possible, take the adult dog with you to pick up the puppy. It will be introduced to the puppy in a more neutral environment and may warm up to the puppy quicker.
Hold the puppy in your arms and show them to the adult dog. Say the adult dog's name and identify the puppy as its, such as "Barkley's Puppy." The dog will understand that the puppy is part of your pack. He should understand that the puppy is a new part of the pack and understand this fact.
If your adult dog is being too aggressive towards the puppy, you may want to consider getting help from a professional dog trainer or dog behavioral clinic.