Dropbox integration will not be available for a while once we completely disable old web manager environment.
We're already working on a new and much better Dropbox integration, which will allow you to connect specific Dropbox folder with an Avocode project. It will also automatically recognize and sync design revisions.
We should be releasing that newly improved feature shortly after the 3.0 version.
While the web environment is still working, it is possible to upload design directly from Dropbox. Just choose the option to upload a design from Dropbox in this menu in our web manager:
The Dropbox chooser will instantly appear and you just have to choose which file you'd like to import.