When you want to learn how something is done, it is often very useful to observe that thing actually happening. This holds true for learning about communicating with others by being in a work environment.
When you are in a work environment, people are communicating with one another all the time. You will see people communicating with customers. You will see them communicating with suppliers. You will see them communicating with subordinates, peers, and superiors. From all of this communication, you can start to understand how you, yourself, should communicate.
From being in this environment, you can learn what sorts of body language people display when talking to various other sorts of people. You can learn what types of words and what level of formality are deemed to be appropriate in various situations. You can see what sorts of interactions leave both parties feeling satisfied and what sorts of interactions lead to hard feelings.
In short, you can learn almost anything about communication in a business setting simply by being in such a setting and being observant.