Connect an external hard drive or SSD
Open System Settings
Click General
Click Time Machine
Click Add Backup Disk
Select the backup drive
Turn on Time Machine backups
Wait for the first backup to complete
Keep the drive connected for automatic backups
Use iCloud to sync important files
Copy important files to an external drive manually
Use Finder to drag files to a backup folder
Create a bootable clone with third-party backup software
Verify the backup by checking recent files
Store a second backup in a separate location