This article is part of a series related to course discussion boards. For more information, please also see these related support articles:
This is an excellent resource from dropbox on how to upload a file and create a shareable link: https://www.dropbox.com/help/167
Once you have created your link, simply paste the link in your post or reply on the discussion board and it will be automatically converted to a clickable hyperlink. Other students can then click that link to access your file.