As far as installing it this is the way I did it. I unpacked it in my /opt(You can put it where-ever u like)directory. Then ran the CL and started firefox.
Code:
/opt/firefox/firefox
This checked to make sure everything was updated.
After that I just created a link to firefox.
Not sure why it isn't like most software where you have to install it but maybe someone else can answer that.
For the Icon that depends which GUI your using. If KDE then just right-click the icon select prop, then click the icon and change it.