What do I do if I feel that I am familiar with the course material for a particular class and do not wish to take it?

This is called challenging a course and you must be a matriculated student in order to do so. If you have already earned a grade in the particular course or are currently registered in the course, you cannot challenge it. You can see if a course can be challenged by contacting the department chair of that particular academic area. If they agree to process the challenge, you must take and pass an exam.  Various fees will apply.