Creating new webapp on new instance generates errors.

Errors:

Unknown SQL Exception 262 occurred. Additional error information from SQL Server is included below.  CREATE DATABASE permission denied in database 'master'.

Database 'master' on SQL Server instance 'servername\newinstancename' is not empty and does not match current database schema.

In my new instance, I've gone into the Databases > System Databases > master > Security > Users, and granted my SharePoint Admin accounts with Database Role memberships of db_owner and db_securityadmin, but I'm still getting errors.

I'm trying to create the new Web Application through CA, /_admin/WebApplicationList.aspx, using Database server servername\newinstance , I'm getting Master DB errors related to the above.

Thanks,

Scott