by Ken Saunders
Installing Firefox Add-ons is quite easy. Simply follow the steps below and in no time you'll be using your new extensions and themes.
Also see, Manually Install a Firefox Add-on. Learn how to install a Firefox add-on from a downloaded extension or theme file.
First, go to the Firefox Add-ons site and select the extension or theme that you would like to install.
Click on the Add to Firefox button and the Software Installation window will appear after the add-on has been downloaded.
After a brief countdown (takes about 2 seconds), the Install Now button will be active. Click on Install Now.
Some add-ons (restartless ones), do not require restarting Firefox after installation. For those, a small popup may appear notifying you that the add-on has been installed successfully.
Add-on Options Once Firefox restarts you will now be able to use your add-on. Many add-ons provide new interface objects such as buttons, toolbars and various options. See the Firefox Add-on Options page for more information.
Related: Customizing Firefox Customizing Toolbars