Your question is not clear. You say that you want to give permission to new user in the prodcution database. But in that case, why do you mention the fact that you copied it to the development server?

Also, are talking about an SQL login or a Windows login?

And what permissions do you want to assign? To permit a user to access a database at all, you do:

USE master

go

CREATE LOGIN [domain\someuser] FROM WINDOWS

go

USE mydb

go

CREATE USER [domain\someuser]

The user will now be able to access the database, but unless you have granted access to public (and you shouldn't), he will not be able to see or modify any data in the database.