GPO to make domain user as local computer admin

1. Go to Group Policy Management Editor.
2. Expend Computer configuration\Policies\Security Settings\Restricted Groups
3. Right click and hit "Add Group"
4. Type "Administrators" and hit "OK"
5. Click "Add..." under "Members of this group:"
6. Enter the users
7. Click "Add..." under "This group is a member of:"
8. Add the "Administrators" Group. (You may also add the "Remote Desktop Users")
9. Hit "OK".