1. Locate http.conf, and open in an editor
Likely location /etc/apache2/
2. Uncomment the following line (remove #), and save
#LoadModule php5_module libexec/apache2/libphp5.so
3. Locate DocumentRoot
Scroll down a bit, should be something like (might be a different path?):
DocumentRoot "/Library/WebServer/Documents"
4. Navigate to the Document Root, and create a new folder there (e.g. chat)
5. Dump the contents of chat.zip there
6. Start apache
in a terminal: sudo apachectl start
7. In safari, navigate to http://localhost/chat/chat.htm