I'm trying to install the Google Sitemap Generator 2 and have Dreamweaver CC 2015, but when I try to install it I get an error message that reads, "This extension cannot be installed. It requires Dreamweaver version in range of inclusively between 12 and 15." Not sure what that means or if there is something I can change.

Please use the DMXzone Extension Manager to install your extensions.

That is where I am trying to install it from and get that error message.