under the fancy Download Firefox link, is a link for Release Notes
that detail the install process.
you can install it where ever you want really, /usr/local is where I put it. then I put a symlink to /usr/local/firefox/firefox (the shell script that runs FF) in /usr/bin which is in the PATH.
you might want to read the man pages for tar
I wish other apps were so easy to install on linux, but I guess I'd rather try compiling it myself if it meant it would stop crashing all the time.