Backing up files from a network location is achievable with Just Cloud. There is an add-on for this ability that you can purchase from your Control Panel on the web app. If you have files located on a network that you wish to backup the process is slightly different to regular file selection.
On Mac the network drives you have access to appear in the manual selection window.
On Windows the process involves a bit more clicking:
If this process is unclear it may be best to consult your network administrator for more help.
Network Drive Backup is 99.95 per year, however, without the add-on, you can still drag and drop files onto the app from a network location and they will be backed up.