How to add a Super Admin?

[New Joe]

I would like to add another user id to the Super Admin how to do?
When the Admin who isn't Super Admin tries to add permissions all I see is this:

Sorry, you are not allowed to edit administrator permissions.

If you think you should have permission to access this page, you will need to edit the $config['SpecialUsers']['superadministrators'] variable in the includes/config.php file.

To allow the administrators to access this page, edit the variable to include the user IDs of those administrators should have access, separating each user ID with a comma, like this:

$config['SpecialUsers']['superadministrators'] = '1,25,57';

To allow only a single administrator to access this page, simply add that user's ID with no commas, like this:

$config['SpecialUsers']['superadministrators'] = '1';

Can anyone give me advice how to do the above please.