Hi partner,
If your db means new organization in D365 on-premise, you must be a member of the domain where D365 is installed, you could not add an organization as a member of a child or a trusted domain.
If your db means adding new entities, you just need to give the account right permissions in D365.
If your db means Business Central dbs, you could refer to this doc.
https://docs.microsoft.com/en-us/dynamics365/business-central/dev-itpro/cside/cside-create-databases
If my understanding is not correct, please kindly share more details.
Hope it helps.
Best Regards,
Leo
Hi Brownie,
To create a database, you must be an administrator in the selected environment, and the appropriate license must be assigned to you. This article explains how to create a Common Data Service database.