Make sure that you have the latest updates to the extension manager installed.
Before installing the new Data Bridge 1,2,1 version, you should uninstall it from the extension manager.
After installing the extension to the extension manager, when you open Dreamweaver, it should launch the WebAssist installer. If the web assist installer does not launch automatically, open a php page to force it to launch.
after the web assist installer completes, make sure to restart dreamweaver.