Simply get the ChromeID from the Chrome website and input it into the tool.
e.g ThreatPinch Chrome Extension URL https://chrome.google.com/webstore/detail/threatpinch-lookup/ljdgplocfnmnofbhpkjclbefmjoikgke/related
All we need from that url is this part "ljdgplocfnmnofbhpkjclbefmjoikgke"
Usage
./ChromeCRXdownloader.sh
It will then prompt you to
Input the ChromeID e.g ljdgplocfnmnofbhpkjclbefmjoikgke and then
Input the output filename e.g ThreatPinch.crx
Done.