This question already has an answer here:
"It works! This is the default web page for this server. The web server software is running but no content has been added, yet."
I have read a few things on the internet on this topic, and now I know that I should be able to write my php in documents that are stored in filesystem/var/www/ but I cannot create documents in there - apparently because I am not logged in as root. Could somebody help me with that?
Also please note that I have very little (if any at all) knowledge of linux so please make it comprehesnible for such an uninitiated user as I am.