You should contact the addon creator on how to use and install their software.

''<p>Richard Crossley [[#question-1478483|said]]</p>'' <blockquote>How do I actually install the Surfshark extension, because everywhere I go just seems to be information about the extension, but nowhere to click on to actually to install it ?? </blockquote> Are you referring to the Surfshark VPN Extension? https://addons.mozilla.org/firefox/addon/surfshark-vpn-proxy/ and click on "Add to Firefox"