Automatically, File History is switched off, so open the beginning menu and click on 'Settings'. Select 'Update & security' and select 'Backup'.
Then click 'Add a drive' to select which exterior drive to keep your backups on - this could include NAS drives or USB drives connected to your router (simply click 'Show all network locations' once the link seems).
You'll also visit a mention of the 'Go to Backup and Restore (Microsoft windows 7)' - if you've upgraded from Window 7 and wish to keep using that old backup tool from that form of windows, you can jump to step six.