Using Classic Outlook on Windows for personal email, calendar, and contact management
The New Outlook - either Outlook Pre or Outlook on the web - does not have a File tab. If you want to use the old, good Outlook (which is much better at the moment) you need to turn off the new Outlook switch in the title bar. You can use both - pin Outlook Pre to the taskbar then turn it off and use the good one.
Or type Outlook on the start menu and open it, not Pre. You want the Outlook that does not have Pre on the icon and lists the new items under the icon.