Start by opening a Linux shell. You can start KDE's Konsole by clicking on the terminal icon in the Kicker panel or by running konsole from your <Alt+F2> quickstart.
There are many ways to start a shell with your system. Other terminal programs include xterm, rxvt, and eterm, just to name a few. Konsole just happens to be KDE's terminal application.
From the shell prompt, why not try entering each of the following commands? Notice what they do.
A few simple commands
Date and time.
Show me how much free space my disks have
Who is logged onto the system?
Similar to who but with different information.
Show me a calendar
Identify your workstation.
Hello, ello, llo, lo, o, o, o . . . .
Try typing: echo "Hello world."
Who last logged in and are they still logged in?
You may need root access for this one.