It's hard to tell exactly what your professor is looking for without knowing what texts you will be referencing. However, here is a general breakdown of what the question is asking:
When you learn to write creatively, as in fiction writing, you are learning the craft of writing. This means you are learning how to create interesting characters, build tension, control plot arcs, create sensible linear plots, create rising action, have a climax in your story, have falling action, and plot resolution. As you become more comfortable in how to craft a piece of creative work, you become more secure in these skills. Eventually, these skills transfer to your critical thinking, and when you read a story you will begin to notice how the author crafted the stories and what techniques the author implemented.
For example, you may read a book and notice a character is acting strangely. Rather than simply discounting this information and continuing to read, you may pause and consider, why is this character acting strangely? What is the author trying to tell us with the character's behavior? What might this character end up doing in future chapters? All of these mental checks and questions are part of a critical thinking process you go through as you read. Creative writing often helps you hone and refine your critical reading eye because when you write creatively, you must turn this eye to your own writing.