For adding a co-administrator the Howto refers to a "Hosted Services, Storage Accounts & CDN" view. But I can't find anything like this in the new portal.
Does anyone know how to do this in the new portal? Is there a way to login to the old portal?
The "classic" portal (manage.windowsazure.com) has been retired. Co-admins are managed through the portal.azure.com site now. To manage co-administrators: