This extension adds a tiny icon on the status bar which notifies you when your friends update their tweets. Also it has a small text input field to update your tweets.
After installing TwitterFox in your Firefox, TwitterFox icon appears on the status bar with gray icon. Click the icon to open setup preference panel. Click ”Add account” button to enter your user name and password. Then click OK button to login Twitter. When your friends update their tweets, TwitterFox pops up small balloon on right bottom corner on your browser window.