PHP problems??

I'm trying to work on a friends website that seems to have been done with PHP. I only know HTML. How can I edite the pages so i can add things to them or even add another page and update all of them. I don't even know where too look?? Can someone help please.

PHP is a simple scripting language and the best resource for it is it's origin: this site: http://www.php.net/

You can edit PHP pages with just Notepad. No compiler needed. You will need to have PHP installed and linked to your webserver software. This can be Apache, IIS or even any other custom webserver software. The biggest problem is just configuring the server properly but once it's working, you can put your attention to writing PHP code.