Open Thunderbolt, open the tools in the toolbar, and find browser support->; Add Firefox support.

If you are prompted that you can't find the Firefox installation directory, click Yes to find it manually.

Usually the default installation directory is:

c:\ Program Files \ Mozilla Firefox \

Find the back point and click firefox.exe.

Fokko will open a software installation pop-up window "Select the following items to install"->; Thunder.xpi (unsigned will be displayed). Finally, just click the Install Now button below.