Download the XPI file
Visit the Downloads page for the latest downloadable XPI files.
Please note the following:
The folder location to which you download the file
The name of the XPI file, for example:
ai-sidebar-1.0.0-beta.1.xpi
Install within Firefox
Once you have downloaded the XPI file, follow these steps:
From the main menu in Firefox, go to Tools > Add-ons
At the top of the Add-ons Manager page, select the “Tools for all add-ons” button (the “gear” icon), and from its menu, select “Install Add-on From File…”
In the “Select add-on to install” dialog, select the downloaded XPI file and choose “Open”
An Add-ons Manager dialog box will appear – select the “Install Now” button
When prompted, select the “Restart Firefox” button