You can find all of your courses in your Dashboard once you are signed in.
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 as the top banner, with a button labeled "Resume".
Any other course or community you're enrolled in will be arranged by category below.
You can revisit any course that you have current access to and jump around to any section you need to review again.