After the secondary installer runs you need to restart Dreamweaver. Open any web page and it should run a secondary installer with three steps that pops up on the screen. After that runs you have to restart Dreamweaver. If you don't do those things the menu options won't work.
To convert from MySQL to MySQLi, just go to the site you want to convert and add a new MySQLi connection through the database panel. Once you have the connection made and working (test it with the test button). Then you can open any recordsets, insert, update, or delete server behaviors and change the connection from your old MySQL connection to the new MySQLi connection and the code should be updated for you.