Download the latest TEBE by clicking
this link. In the download window that Fx brings up, the file name to save is listed as "
tebe@guid.softwarebychuck.com.xpi.zip". Remove the ".zip" at the end and save the file as "
tebe@guid.softwarebychuck.com.xpi".
In Thunderbird, click
Tools > Add-ons > ("gear" icon) > Install Add-on from file.... Navigate to where you saved
tebe@guid.softwarebychuck.com.xpi, double-click on the name and follow the prompts to finish the installation.