Adding a Revision
When you want to add a new revision for a file you've been working on to show the changes, you can upload new versions. To upload a revision of a file, click the file and view it in the presentation screen (where you would make notes). On the top header navigation, there's a "REVISIONS" link which will have a drop down menu for you to upload a new file. Once you have uploaded the new file, the old version becomes the archived in this drop down (so you can reference if you need to) and from now on, you will only see the latest version of that file.
Now you're project has revisions. Also, on the dashboard, files that have revisions look like the rest of the thumbnails, but only stacked (so it looks like other files below it). Easy way to spot revisions.