Programmatically set a DB user to be db_owner

To give the user DBO permissions:

EXEC sp_addrolemember N'db_owner', N'[Driver-SOC-ChrisTest]'

To make the user owner of the database (not advised):

EXEC sp_changedbowner N'[Driver-SOC-ChrisTest]'

I quite often go into the GUI, make the changes I need and then rather than saving by pressing OK, I press the Script button at the top of the dialog and send it to a new window.

This would give you the code the previous poster provided.