You type that in a terminal, mate.
If you're in KDE, there's a thing that
looks like a monitor with a shell ... click
If you're in Gnome I have no idea
what it looks like, but pretty likely like
a monitor... click that.
If you're running some other Window
Manager, find something that says
term in its name, like xterm, aterm,
eterm, ... :)
Alternaltively, press <Ctrl>+<Alt>+<F1>,
log-in and tackle things from there...
To go back to your graphical screen