Head to the latest release and download the
cb_thunderlink.xpi from the assets. You can install the
cb_thunderlink.xpi in Thunderbird using the
install add-on from file feature in Thunderbird.
When not using the OS-integration and the
clickable feature, that is all you need.
You can start using
(cb)thunderlink's with the approach of copying the links and pasting it using the cb_thunderlink button.
If you need the full power of OS integration and the possibility to click links, read further. The instructions will be different per OS and currently only Windows is supported.