Manually add the user accounts that you want to back up to the user group.
If you have different backup requirements for some user accounts, you can create user-defined user groups for those user accounts. For more information, see Creating User Groups to Back Up Specific User Accounts.
From the navigation pane, go to Protect > Applications > Office 365.
The Office 365 apps page appears.
Click the OneDrive for Business app.
The app page appears.
On the User groups tab, right-click default, and then select Manage.
The default dialog box appears.
On the Users tab, click Add user.
The Add new content dialog box appears.
In the User account column, select the user accounts that you want to add.
Click Add, and then click Save.