You can find all of your courses in your Dashboard once you are signed in. Note that individual product pages may appear as if they're asking you to pay again; those are the public pages, you'll find your courses in your Dashboard.
When you sign in, you should be automatically taken to your Dashboard.
If you're not automatically signed in, click on your account info in the upper right and select My Dashboard.
The last course you were working on will be displayed first, after any communities you're a part of.
Members enrolled in multiple courses can use the search bar and/or filters to quickly find a course.
You can revisit any course that you have current access to and jump around to any section you need to review again.