Navigate to where you saved the extension, and double click it. (You must have the Macromedia Extension Manager 1.6 installed at this point.) The extension manager should automatically open, and begin the installation process. You will receive a disclaimer message like this:
You must accept the terms to install the extension; otherwise installation will abort. After you click Accept, the extension will install & you should see the something like the following:
Now, you can restart Dreamweaver, and you're ready to go on to the Usage section.