The clicker is a very effective training tool, that when conditioned with a reward like food, a treat or a toy signals to your puppy that he has done something right. The clicking sound becomes synonymous with the reward/treat once training has begun. However, your puppy has to be taught that the clicker means something and clicking alone is not reinforcing anything.
If your pup barks: Some dogs have the habit of barking at other dogs while on a walk. Oftentimes, this behavior comes as a result of lack of exercise. Make sure your dog gets the proper amount of mental and physical stimulation for his age and breed. If this is still a problem, use the same process as you would if your dog is lunging, as described above — create distance and offer treats before he starts to bark, so every time he sees a dog he gets used to turning his attention to you.