Home already is the default tab; you shouldn't be able to view messages from the File tab as this takes you to account settings and options.
I think the issue is the ribbon bar is not appearing automatically -- in Outlook 2013, the File tab is a solid color while all the others have white backgrounds. With the ribbon bar missing, it just looks like you are in the File tab.
To fix this, click on any tab and the ribbon bar should drop down. Off to the far right is a little icon that looks like a pin -- click on it. This will make the ribbon bar appear every time you open Outlook.