Log into your carbon server. https://172.16.1.123:9443/carbon/
Default user:password is admin:admin.
Go to Multitenancy > Add new tenant and fill in all fields.
Save and go to https://172.16.1.123:9443/emm and login with your new credentials. In my case email@example.com and the password I picked.
I got an error here when the site redirected me to localhost instead of the IP-address, I solved this in a manner not found in the documentation so it might be ugly and non-recommended. Anyways: