I agree with sandyd's advice above. Here is a tutorial that explains a bit more about installing software in Ubuntu, and why we do not generally install apps the "Windows way" of surfing the web and downloading untrusted installers from random websites. Rather, the Ubuntu Software Center is kind of like the Apple App Store, where you can easily install thousands of trusted & tested applications with a few mouse clicks.
If you really, really want to follow the instructions on the Barry website (which I do not recommend at this stage in your Linux learning) you have made a big mistake already, which is that you are not running Debian Squeeze. As the instructions say, you must use the correct repos for your release, which would be in your case:
If you must edit the important system file /etc/apt/sources.list then be very careful!
deb http://download.barry.netdirect.ca/barry-latest/ ubuntu1204 main
To reiterate, this is an important system file that the user should not typically need to edit on a regular basis (if at all). How to recover from typos/errors/mistakes in this file is one of the most frequently-asked questions I see on these forums. Be safe and use the Software Center!
gksu gedit /etc/apt/sources.list