You need to ensure that you use Windows Server Backup to back up data to Microsoft Online Backup

You have a server named File1 that runs Windows Server 2012. File1 has the File Server role service
installed.
You plan to back up all shared folders by using Microsoft Online Backup.
You download and install the Microsoft Online Backup Service Agent on File1.
You need to ensure that you use Windows Server Backup to back up data to Microsoft Online Backup.
What should you do?

A.
From Computer Management, add the File1 computer account to the Backup Operators group.

B.
From the Services console, modify the Log On settings of the Microsoft Online Backup Service Agent.

C.
From Windows Server Backup, run the Register Server Wizard.

D.
From a command prompt, run wbadmin.exe enable backup.

Explanation:
http://blogs.technet.com/b/windowsserver/archive/2012/03/28/microsoft-online-backup-service.aspx