Office 365 Business apps are now becoming available for Enterprise subscriptions

Applications only available to Business Premium plan subscribers are starting to be released for Enterprise plan subscribers. Microsoft Bookings is the first now available to E3 and E5 plans. Enterprise plan users can purchase the apps for free in the Office 365 store. Once you have done that you’ll see the application (s) appearing in your app launcher.

To find out more check out this article from Microsoft