Wikipedia:MozEx tutorial
This tutorial describes how to use the "MozEx" extension of Mozilla and Mozilla Firefox to edit wikipedia pages in your editor of choice. It is assumed that you already installed and configured MozEx, and also configured your editor, otherwise please see Wikipedia:text editor support.
To edit a wikipedia page, click on the "edit page" tab on top of the page. A box containing editable text will show up, which is sometimes called text area. Now, right-click with the mouse in the text area, and select mozex→Edit Textarea. Your favorite editor will pop-up, and you will be able to edit the text. Once you are done, save the text, go back to the browser window, and click on the text area. The text will be automatically updated, and the file you just saved will be deleted from your computer.