Click on the + box on the term you would like to add a class.
The Add requirements window opens for the term. The Still needed courses are displayed. Still needed courses are course requirements for the degree you are following that are still needed.
Use the scroll bar on the right side of the window to scroll down and view classes still needed for your degree.
Check the box next to the classes you would like to add to your plan for the selected term.
When you are done adding classes, click the ADD TO PLAN button.