Twitter for WordPress Extended shows your tweets, tweets for a search term (e.g. a tag), your friends timeline or the current twitter trends.
Drop "twitter-for-wordpress-extended" folder (or even twitter_extended.php) into /wp-content/plugins/ and activate the plug in the WordPress admin area.
If you use the "Twitter for WordPress" plugin please deactivate it before activating "Twitter for WordPress Extended". The extended plugin is designed to replace the original.