To those users that have had problems installing extensions and themes, I hope the guide helps. It starts off very basic just so no-one is left out. I have tried to write this so it would be understandable to some of my computer illiterate, if you don't follow any point please email me as it means I have failed this aim. This applies to Firefox versions 3.0 and up, and any version of Thunderbird or Sunbird.
Terminology note: when the word "add-ons" I mean both extensions and/or themes.
1. Firefox The Normal Way
It is presumed at this point you have found an add-on that you want to use, and are wondering how to do so. First naturally you click the installation link. Hopefully you don't get the Downloads opening. If you do go to 2. Firefox, if it prompts for download. Else you may get something like this.
If you do, press the accept button. There is a chance that if your downloading from a trusted site, such as the offical Mozilla add-ons site, it will now show this.
The Install Now button will be disabled for a few seconds before you can click it. Just wait for it to be done then press this button. You will then be presented will another window where you will see the add-on downloaded and installed. When a yellow bar appears you can click the "Restart Firefox" button, like shown below. You may also just continue browsing the web or installing more add-ons. The add-on will be installed next time Firefox is started. Now your done, no need to read any further.
2. Firefox, if it prompts for download
If the web site is not correctly configured - extension developers see these instructions on how to configure you site - Firefox may prompt you to download the add-on instead of installing it. Like show in the below image. Just save the file somewhere easy to find, like the Desktop or Documents folder.
Press the "Save" button down the bottom right of the window, and the Download window will open. Once this is completed go to 3. Install a saved add-on file.
3. Install a saved add-on file
There are a few ways this can be achieved. For extensions, if you go to the File menu, then Open File and select the extension's .xpi file or the themes's .jar file and open it. Firefox may prompt you to install it. If it does, the process is much like above.
If you prefer or you must, you can also use drag and drop. First open the add-ons window - click the Tools menu then Add-ons like show below. The window has multiple tabs, make sure you in the one that matches what your trying to install.
Then open the folder that contains the add-on you want to install, click and drag it into the add-ons window. When you let the mouse button go, it should prompt you to install the extension or theme as detailed above.
The last option I can give you is to use the button from my Toolbar Buttons called Install which can be used to install add-ons. You can also just download the Install button. Then just put it on your toolbar and click it, select the file in the window that comes up, and it will install it for you much like normal.
4. Installing for Thunderbird or Sunbird
Installing an add-ons into Thunderbird has a few more steps, but also is more straight forward. To start you need to get the extension downloaded to some place on your computer. If when you click the link it prompts you to install it, don't. This would install it into Firefox. If it does you need to right click (click with the right mouse button) the link, and press Save Link As, like shown below.
Then save the file to some location that you will easily find again, such the the desktop or Documents folder.
What you now want to is go to the Tools of Thunderbird, Sunbird or what ever your trying to install it to, and press Add-ons.
Make sure you in the correct tab and press the install button and shown below. Then select the file to install.
Then in the window that comes up, wait till the Install Now button becomes enabled and click it.
Finally find the restart button and click it. The extension is installed next time the application starts.
Disclaimer: All screen shots were take of Firefox and Thunderbird running on Windows XP, which was being run in a virtual machine. Codefisher.org does not approve of the use of Windows in general and recommends Ubuntu Linux. Windows XP was chosen because some buttons are located in slightly different locations, and I need the tutorial to be as easy to follow as possible by my largest user base.