Extensions allow you to easily add new features to Adobe applications. Extensions extend the functionality of the product to enable you to do more with it. An extension package (MXP) file is compressed installation file containing the extension(s) to be downloaded and installed by the Macromedia Extension Manager. The Extension Manager is a free program that lets you easily install new extensions and keep track of the ones you already have. Download the Extension Manager installer and save it on your local drive, then double-click the installer to begin the installation process.