Change Time Machine Configuration preferences on Mac
On your Mac, use Time Machine Configuration preferences to choose where your backups are stored.
To change these preferences, choose Apple menu > System Preferences, click Time Machine, then click Select Backup Disk.
This list shows the disks or partitions you’re using for your backups. To stop using one, select it, then click Remove Disk.
This list shows the disks or partitions available for your backups. Click the one you want to use, then click Use Disk.
Other AirPort Time Capsule
To use an AirPort Time Capsule for backups, click Other AirPort Time Capsule, then click Set Up. Follow the instructions in AirPort Utility to set up the AirPort Time Capsule, then return to Time Machine preferences. Your AirPort Time Capsule will be listed as an available backup destination.
Protect your backups from being accessed by unauthorised parties. If this tickbox is dimmed, the selected disk doesn’t support encryption.
If you upgraded to macOS Catalina on a Mac that uses a Time Capsule or other network storage device as the backup destination, your existing backups are also upgraded and can be used only on macOS Catalina. New backups that are created can be used only on macOS Catalina.