How Can Carl Jung’s Theory of Archetypes Help You in Your Creative Writing?

Among his many theories, Carl Jung includes “archetypes”. An archetype may be defined as “a universally understood symbol or term or pattern of behaviour”.  If you read Robert McKee’s Story, you will find that the key to writing a great novel lies in “building archetypal elements into the story.” So what exactly are these “archetypal elements”? And how exactly can they help creative writers?