to import a backup on an iPhone:
- install Delta Chat on the iPhone
- connect the iPhone to a Mac computer
- open the Finder on the Mac
- navigate in the Finder to your iPhone on the left
- then select “Files” at the top
- drag’n’drop the backup .tar file to “Delta Chat”
once done, you can disconnect the iPhone from the Mac.
on the iPhone:
- open Delta Chat
- select “Log in to your server” on the welcome page
- tap “Import backup”
- the backup imported from above should appear, tap “Ok” then.
note: on older Mac’s (before 10.15 Catalina), you have to use iTunes instead of the Finder, the rest is more or less identical.