[Eikinskjaldi]

Instructions don't come much clearer that this.

"To allow the administrators to access this page, edit the variable to include the user IDs of those administrators should have access"

not usernames, userids. and not semicolons, but commas

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

As for an editor, I use vi, but I am assuming you are using a windows system and accessing the site via ftp, in which case I would recommend bbbedit, although there are a host of syntax highlighting code editors out there, some of them for free as well.