Assuming you're used to Windows, you can think of a shell as a command prompt. Start it with Alt+F2, typing in
konsole. A black screen then appears with a promt at which you can enter commands or run programs. Now type in
krandrtray followed by enter and you should get a new system tray icon. You can now exit this shell with
exit.
You could also have done it by starting krandrtray directly from the Run Command screen, but now you also know how to start and use a shell