Use the Project 7 Extension manager http://www.projectseven.com/products/ex-man/info.htm
or the DMXZone Extension manager https://www.dmxzone.com/go/22670/dmxzone-extension-manager-for-dreamweaver/
They are both free and work to install extensions into Dreamweaver cc
Dreamweaver dropped support for the extension manager in the more recent Dreamweaver versions