As far as I know, there's nothing you can do to "make it accessible." Just create a directory inside your own home directory called "public_html" and it may become accessible via eg
http://cas.mcmaster.ca/~mattinui. If it is, then you can just drop your HTML and whatnot in there and treat that directory as the root, just like eg /var/www/html on some other Linux distros. Right now it seems that the webserver is denying access, at least for my account, but I've had it working before. It just depends on how they have the server set up.