There is nothing you need to do to activate the tabs in File Explorer, as long as you've installed the Windows 11 2022 Update and its subsequent updates released by Microsoft up to November 2022.

We show you how to disable Tabs in File Explorer on Windows 11 by using a free command line tool called ViveTool.

To restore Tabs in File Explorer after Restart in Windows 11, enable the 'Restore previous folder windows at logon' setting in Folder Options.

File Explorer finally has tabs—but you'll have to join the Insider Preview program to try them out.

Besides, the tabbed File Explorer itself is a one buggy thing that is not available for all users. If you want to try it, learn how to enable tabs in File Explorer in Windows 11 here.