So you have a previously downloaded course (as a .zip file) and you wanna upload it to the course builder? Also easy!
Just click and drag the file from your desktop to the template selection area at the top of the page. A white border will start flashing to show you're in the right spot.
Drop the file anywhere in here. The course will then be uploaded to the course builder, appearing at the top of the course list.
This will only work with .zip files downloaded from the Course Builder. Files downloaded from other Ninjas (Media, Document, etc) are not compatible and cannot be uploaded here.