I'm also 'just' a graphic designer, but perhaps I can help you a bit: First, you should have a /usr folder; all Unix machines do. If you're looking in the Finder, you won't see it since it's a shitten directory. Go to the Go menu and choose Go to Folder, and type in "/usr" minus the quotes and it should make it visible for you. Or, in Terminal, type in "cd /usr", again, minus the quotes. For my machine, I had the /usr/share/httpd/ path, and just had to make a new folder called conf within that. The Terminal command for this is "mkdir conf" while within the httpd folder.
I'm not sure why you're having trouble with the htpasswd command; perhaps check your spelling?