System Preferences > Time Machine > Pick you External Hard drive
Why Use Time Machine?
- it keeps hourly backups for the past 24hours
- daily backups for the past month
- weekly backups for all previous months
- the oldest backups are deleted when disk becomes full
Great way to make sure everything is saved externally incase anything every happens and the best part is, its automatic once you hard drive is plugged in so you don't have to worry about it. If anything happens, everything is stored to then restore your computer. You can see below all the backups that you can scroll back into to find something (photo, document, music, file, etc)