If he's using Mac OS X (or Linux, but then he'd probaby know this - Linux users know things...) the .rockbox directory could be hidden in the file browser, like it's supposed to on *nix systems with dot files and dot directories (OS X'es underlying OS is Darwin - a modified FreeBSD if I understand correctly). The solution is whatever the filebrowser used has for "show hidden files".
Anyways; You're supposed to create a "doom" folder inside your ".rockbox" folder which should reside right on the root of your player and then put the needed files there.
And if you're using Windows: / means the same as \ does on Windows. OK?