As a teacher, go to onCampus:
  1. Select your Class from the Classes menu
  2. Select the Assignments Tab
  3. Click + Assignment
  4. Select Downloads to the right of Attachments
  5. Click Browse
  6. Select a Document and then choose Open
  7. Add a Description
  8. Click anywhere outside of the Description Text Box and another Browse option will appear so that you can add additional files
Note: You can also upload Zip Files if you have a large number of files and do not wish to add them one at a time