How to create database, and add user linked to login?
Not sure how dbo is coming into play. Here is how you create a user in a database mapped to a server login, whether that login is already associated to a user in any other database:

CREATE LOGIN foo WITH PASSWORD = 'bar', CHECK_POLICY = OFF;
GO
CREATE DATABASE splunge;
GO
USE splunge;
GO
CREATE USER foo FROM LOGIN [foo];
GO
-- then permissions:
GRANT ... TO foo;
EXEC sp_addrolemember N'&lt;role&gt;', N'foo';
etc.