A very common question when dealing with OneDrive for Business (ODFB) is about how to add additional administrators to ODFB sites. One option we have to do that task is to use the options available Administration SharePoint Online in Office 365 :
Access the SharePoint Online Administration and in the vertical menu, click on “user profiles”. Then click on “Manage user profiles”.
In the page that opens, locate the user profile for which you want to add an additional administrator for ODFB and expand the available options in the context menu. Click on “Manage site collection owners.”
In the popup that opens, you can specify additional administrators for ODFB.