Apart from options to install Firefox using the Debian APT system, i.e. as a .deb package, you can install from mozilla builds. Using the terminal only, the process can go like:
wget -O FirefoxSetup.tar.bz2 https://download.mozilla.org/?product=firefox-devedition-latest-ssl&os=linux64
sudo tar xvf FirefoxSetup.tar.bz2 -C /opt/
This will install the files in /opt/firefox
. If you want a different folder, e.g. firefox-devedition
then you can instead extract the files locally, and move/rename the extracted directory firefox
:
tar xvf FirefoxSetup.tar.bz2
sudo mv firefox /opt/firefox-devedition
You can determine the URL for the product you need by selecting your product on the Firefox downloads page. Then right-click the Download button to copy the link.
To add a launcher in your menu system, see this answer.