CREATE LOGIN of windows user and GRANT SYSADMIN Access

Using below command you can create a windows login and grant SysAdmin access. Replace DOMAIN\LOGIN with windows login name 

USE [master]

GO

CREATE LOGIN [DOMAIN\LOGIN] FROM WINDOWS WITH DEFAULT_DATABASE=[master]

GO

EXEC master..sp_addsrvrolemember @loginame = N'DOMAIN\LOGIN', @rolename = N'sysadmin'

GO

--

Thanks & Regards
Venkat Sangu