The files for the web page are located in /srv/
The problem is that that folder is password protected.
I helped a friend host a landing page on his server, we used the /var/www/ directory as it's not being used by QB and is an obvious place if I forget where the hell I put it.
@bate is right though, you'll need to create an apache .conf file.
If you're willing to put an hour or so effort in it's more than achievable, but if you balls it up you might end up having to rebuild your server (because apache can be a little bit of a pain sometimes).
Backup, Backup, Backup then read:
The short summary is:
put web files in /var/www/html/
create the .conf file in /etc/sites-available/
enable with a2ensite
reload with service apache2 reload
Hope everything goes to plan.
If apache falls on its face after making the .conf file, use a2dissite and reload again.
I'd avoid editing any of the quickbox .conf files as you'll probably make things worse...