There should be a .mxp version that will install in earlier versions of dreamweaver and a .zxp version for more recent versions. I'd stick with the more recent one.
Once you install with the extension manager, you will need to open dreamweaver and open any page. That will initiate the second half of the installation process. At the end of that you will need to restart dreamweaver one more time and the menu access points should start working.