What do you mean by user's private database?
iCloud database is only accessible to its user, not to developers. We even do not known user's account address.
The app is empty after startup, where do I find cloud sync option?
If the app is newly installed on the phone or pad, please try to add some contents by copying from other apps. After that, touch and hold on some content to bring up the settings options.
Last modified: 23rd Oct, 2020