You should start socializing your puppy as early as possible. Ideally, socialization begins before you bring your puppy home. But, you don’t have a lot of control over that. Most puppies are adopted when they are between 8 and 16 weeks of age and this is the perfect time to start or continue socializing your puppy.
Socialization is also not something that stops once your puppy grows up. It’s something that should continue, along with training, throughout your dog’s life. Your dog is your companion and you should continue to do new things and experience new things with them. You and your dog will both be happier for it.