tar xvzf firefox-18.104.22.168.tar.gz
If it runs fine, you may wish to move it to some other place and link it so it its visible to every user, like to opt:
mv firefox /opt/
ln -s /opt/firefox/firefox /usr/bin/firefox2
Note1: The file name (firefox-22.214.171.124.tar.gz) is a suggestion. Substitute with the correct name for your firefox
Note2: I am linking firefox as "firefox2" to do not conflict with any firefox you have previously installed.
Note3: It usually is a good idea to stick with the firefox provided by your distro to keep consistency. Firefox should update itself anyway...