First: I don't recommend doing this if you are a noob without Linux experience.

But what it means is got to xterm (press ctrl+shift+x for example) and type for example the command: apt-get install offscr-solitaire

It fetches the package from an online repository and installs the application. Instructions for adding the required OVI repository are earlier in this thread.

Do not do this unless you understand what you are doing, so please Google and research this beforehand!