Seem to be missing preferences?

Hi, I installed the LinuxCNC thing on Oracle VM VirtualBox. I was looking at the Linux FAQ at  linuxcnc.org/docs/2.8/html/common/linux-faq.html and it seems I don't have some of the options? It says things like "go to System > Administration" or "System > Preferences" but all I have under System are Bulk Rename, nm-tray, Synaptic Package Manager, Thunar File Manager, and Xfce Terminal. Is the FAQ outdated? How can I access these settings? I especially would like to know if there's a way to turn off auto-logoff, as I'm experiencing a glitch with the aspect ratio every time it auto-logs me off and I log back in unless I restart the entire VM.

Those are Debian Linux issues, so might be better looking on Debian forums for the solutions.
It was long ago since i used Debian so i do not recall how to disable screensaver (BTW you are looking for screensaver as it will trigger the logoff ).