Starting from the home page, click on your username in the top-right corner of the window. This will open your profile menu. Scroll down the menu to find the "Classes" tab. Hover your mouse over "Classes" to see "My Classes". Click on "My Classes."
You will be redirected to a page with all of the classes you have enrolled in. You can click on any of the classes on that page to be redirected to it's class page and resume your class.