The campaign ZIP file containing the MP3s will be created automatically when you start your promo campaign. However additional files such as Word, Excel, PDF and images can also be uploaded to your release via the Release Details Page.
Release Management > Release List > Select Release
To upload additional files you simply click the Files tab just above the track listing:
Click Please click here to upload files, then press Choose File and locate the file you wish to attach and click open.
This file will then be added to your promo campaign and can be located under the File Name section where the ZIP file can also be downloaded.