Properly socializing your puppy is all about exposure.
Dog ownership can sometimes be related to experiences that we have as humans. For instance, when a child is going to the dentist, to school, a zoo, or any other environment for the first time, or meeting someone new, there can be apprehension and discomfort; even fear, as a result of experiencing these new events. However, we do not shelter our children from these events: we encourage them to interact with the world, and we encourage the world to interact with our children. This is known as socialization, and is a vital part of healthy functioning in any social hierarchy- including in the world of dogs.