WordPress.org

1. Download the plugin.
2. Unzip the plugin and upload the directory to wp-content/plugins.
3. Activate the plugin.
4. Go to "Plugins » Add new" to use.

Installing the bookmarklet

1. Go to "Plugins » Add new" and look for a green notice. Under that notice you will find a link titled "Install plugin".
2. If you're using Firefox, Safari or Google Chrome, simply drag the link to your bookmars toolbar. If you're using Internet Explorer, right click and choose "Add to favorites » Create in: Links".
3. Now, whenever you're on a third party website that hosts a plugin, simply click the bookmarklet to bring up the installation window.