According to that webpage you posted, there is a Linux driver. It's nice to find Linux support from manufacturers. The bad part is there's no easy installer provided.

In case you didn't know already, a .tar.gz file is a compressed directory in a file, somewhat like a .zip.

What you want to do first is extract the .tar.gz file. You can do this by double clicking the downloading cnijfilter-mx430series-3.70-1-deb.tar.gz file and selecting "Extract". After you extract the contents of the archive, navigate to the extracted directory. Inside you will find install.sh. Double click it - Ubuntu will then ask whether you want to run the program or not. Say that you want to run the program in a terminal.

Tell us if it works, or if the terminal says anything unusual. If it says something along the lines of must be run as superuser or need root privileges, then you'll need to run it as root. For that...you'd need to navigate to the directory in a terminal and run sudo install.sh.