The mobile app can be downloaded from the following places:
Login to the mobile app with the server endpoint URL at
Navigate to the backup screen by clicking on the cloud icon in the top right corner of the screen.
You can select which album(s) you want to back up to the Immich server from the backup screen.
Scroll down to the bottom and press "Start Backup" to start the backup process.
You can enable automatic backup on supported devices. For more information see Automatic Backup.