Well, you've got two choices there. Either you can play in graphical Linux (KDE, Gnome, etc) and look at all the stuff that there is on the system. Make some folders. Make some files. If you're feeling particularly nerdy, try to make some "Hello World" programs.
When you get settled with the self-explanatory graphical interface, open up a terminal window (most of the time, there's a shortcut right there in your menu bar), and start punching in commands. The greatest thing about Linux is its user-friendly help files. When you're in a terminal, all you have to do is punch in ~$man some program name
and read what it has to say. Plus, the help
command will show you the lowest level control over your system.
One of the first things that I think a user should do in a terminal is this:
... and so on.
If you can learn to navigate through your directories, you can learn a lot. Also, if you want to learn your program names, go to /bin and /usr/bin and just look at everything there in list view. There's a ton of program names in there, and all you have to do is type ~$man program
to see what each one does. You can find all sorts of cool programs in there.
I hope this long intro was helpful.