Elgg Local Install on Mac

I have a Mac and want to create my own social network site. I have used on a webhost before, but no want to host it from my Mac. I have PHP 5.2.8 and Mysql and of course Apache. I have all the Elgg files put in /Library/WebServer/Documents. I have the DynDns connect so it should my domain. So when I go to www.thettyn.com/install.php it just comes up the text and not the install. I've tired to create a mysql database but it doesn't seem to work. Can someone also tell me how to add me. I'm pretty sure you do it through Terminal, but it wasn't working. I'm running Mac OS X 10.5.

Thanks in advance.