To access the administrative features for your subscription, navigate to https://portal.office.com and enter the credentials for your administrative account. This will have been provided to you on initial setup of your service.
If this is your first login on a new service, you may need to use your temporary domain (email@example.com). If you've completed addition of your production domain previously, please use this instead (firstname.lastname@example.org).
NB: If you have forgotten the username or password for your administrative account, please contact support.
Once you've logged in, choose the launcher from the top left of the page, then select Admin.