Changing login email address for office 365 admin (O365 Busines)

[Filewalker]

Dear forum members,
We bought Microsoft 365 Apps for Business. During the registration process we got an extreme unusable email address (Email address removed).
Together with our subscription we also got the 1TB Onedrive space. Now we were looking a long time, how we can use another simple email address (personal one) to login to our Onedrive or to our subscription (0365 admin pannel). Can anyone help us and sow us a way how we can change this MS given email address to access our account and Onedrive?
Thanks very much!

[#2]

You would have to register a domain name if you do not already have one and then verify it with your subscription through the O365 Admin Portal (Settings --> Domains --> Add Domain). Once done and verified, you can then switch your sign-in name to <username>@yourdomain.com.