Dropshare Sync has been retired with Dropshare 5 and the latest iOS versions, and has been replaced by iCloud Synchronisation.
Dropshare Sync is a service provided by Dropshare for Mac to synchronise your upload history across all your devices.
To use this service, you need to sign up for an account Dropshare Sync. It takes only a minute, and you only need to provide an email address and password.
Once you've signed up, log in with your credentials in Dropshare on all the devices you want to have a shared history with. Dropshare will start to synchronise the data then. The initial configuration may take a bit, but you can always see the synchronisation status in the Dropshare Sync preferences.
When you upload a new file or delete an existing upload, Dropshare will inform the server about the change and your other devices will update their history as soon as they synchronise the next time. You're free to amend the synchronisation interval in the Dropshare Sync preferences.