Relying on repos more for software installation with other distros, I found firefox installation a little confusing. I figured the following info consolidated from debian wiki and other forum posts might be useful for installing firefox.
Download package from: https://download.mozilla.org/?product=firefox-latest-ssl&os=linux64&lang=en-US
Extract into /opt such that the firefox executable is located at /opt/firefox/firefox
Symlink from usr/local/bin: ln -s /opt/firefox/firefox /usr/local/bin/firefox
Create desktop entry with following contents (note may want to change version number if applicable) at /usr/share/applications/firefox.desktop
[Desktop Entry]
Name=Firefox ‘‘58.0.2’’
Comment=Web Browser
GenericName=Web Browser
X-GNOME-FullName=Firefox ‘‘58.0.2’’ Web Browser
Exec=/opt/firefox/firefox %u
Terminal=false
X-MultipleArgs=false
Type=Application
Icon=/opt/firefox/browser/icons/mozicon128.png
Categories=Network;WebBrowser;
MimeType=text/html;text/xml;application/xhtml+xml;application/xml;application/vnd.mozilla.xul+xml;application/rss+xml;application/rdf+xml;image/gif;image/jpeg;image/png;x-scheme-handler/http;x-scheme-handler/https;
StartupWMClass=Firefox
StartupNotify=true
References:
https://wiki.debian.org/Firefox