The thing that makes Qubes OS special is the isolation. In addition to @adw’s links, I suggest:
Try to learn how to move things (text and files) between qubes, maybe install software, use a USB device, etc. As long as you avoid messing with dom0, you’re good. You can clone your templates and every qube to make some tests. It is perfect to learn things about Linux.
See also:
I started to work on a “tutorial” but haven’t made much progress recently: Tutorial: connect to a Wi-Fi access point
Another useful document is the following:
It is outdated and sometimes a bit hard to read, but it presents the concepts and goals of the OS.