Review old courses

I would like to re-do a course that is already marked as complete.  How do I do that?  When I go to the course, the start button says “complete”, when I press it just takes me to another button that says “complete”.  I did the course before I was set up to code, to learn the coding environment, but now I would like watch and follow along with the course, but I can’t watch it again because it is marked complete.