To receive an email notification when a new file is uploaded to a specific folder, simply select the folder you would like to watch and right click for the "Watch Folder" menu option.  To disable notifications for a folder you no longer intend to watch, simply right click the folder for the "UnWatch Folder" menu option.

Watched Folder notification emails are limited to one every 10 minutes. The way that is enforced is that each watcher will receive a notification when a new file is added. Any files added to that same folder for the next ten minutes are "added silently" - watching users will never receive a notification for them. Anything added 11 minutes or later (from the first notification) will spawn a second notification ... and so on.

This is intentional so that if you are watching a folder and someone adds 100 files to it - you won't suddenly receive 100 email notifications.