well, that extension does not do anything like the big drop down menu on this site.
that adds other menu items to the breadcrumb section in the navbar.
anyway, please give us the actual link to the extension. please tell us what version of phpbb you are using and a link to your board.
considering you are still having problems getting upgraded to 3.2.2 I am not sure why or where you are trying to install extensions.
I am available for custom work on a donation basis. Please send me a PM with your needs.
Premium phpBB 3.2 Styles
OK, so what's the speed of dark?