Wordpress Buddypress default template dropdown menu on pages?

I am using wordpress / buddypress and the default template / theme.

The pages are in the top menu and I want to add sub-pages to some of the pages (dropdown menu) ... how do I add this? Is there a plugin for it?

Thanks

Solution

here is the plugin am using on my website :

you can see it in action at

www.naijaping.com

if you need any futher help, do let me know