Create Login to SQL Server

CREATE LOGIN reports WITH PASSWORD = 'somethingsecure', CHECK_EXPIRATION = ON

Change SQL Server password

alter login reports with password = 'secure password'

Grant rights to a user in db

use [Database-name]
GO

-- add DB user
CREATE USER [Reports-User] FROM LOGIN [reports]
GO

-- map that user to a role in the db
EXEC sp_addrolemember 'reports', 'Reports-User';
GO