"However, do this step only if you don't already have an .htaccess file there -- this will overwrite whatever you have (you may already have .htaccess for fooling spambots, redirecting file types, or some other purpose, so doublecheck. If it's already there, we'll have to retool a bit, to integrate the user-level access with the existing contents)."
Alas, it turns out there already _is_ an .htaccess file in the public_html.