If the Box for Office plugin is not appearing in the File Menu of an Office program (Word/Excel/Outlook/PowerPoint) try these steps:
In the top left of the Office program, click the File tab.
On the left side menu, click Options.
Click Add-ins and then navigate to the bottom. From the Manage drop down menu select COM Add-In and click Go.
Select the Box for Office plugin and click Ok. The plugin name will reflect the current program you are in. (Box for Outlook, Box.Excel, etc.)
If the plugin does not appear after doing this process, please follow these steps:
Go to the Add-Ins section again. Select Disabled Items from the Manage drop down menu and click Go.
Select the Box for Office plugin and click Enable. Then restart the Office program. You should now see a Box option in your File Menu.