Hello @VernieTrail,
You tagged this question with the "Student" label but @knichols provided instructions for other roles that have edit rights to a course.
What is your role at your institution?
If you are a student, students do not typically have the ability to add files to the "Files" area of a course.
If you are a student, you are probably trying to upload your work (upload your file) as a submission for an assignment. Is that what you are trying to do?
If you are trying to upload your work/file to an assignment, you can do that by following the directions in the How do I upload a file as an assignment submission in Canvas? - Instructure Community - 274 support article.
Does that help you?
-Doug