If you work on multiple computers (e.g., a laptop and a desktop), you may want to keep your code on GitHub so that you can access it from all of them. This page links to step-by-step instructions for doing this in a variety of different environments.
Note that these instructions are generic and are for “unofficial” personal use in courses that don't require the use of Git. Some courses may require the use of Git (and GitHub) and may do so in very specific ways. If so, you must follow the specifications for that course.