Theming the sub menu in dynamic persistent menu

Can somebody teach me how to include CSS on submenu of dynamic persistent menu?
I want my menu to be displayed vertically instead of horizontal sub menu, will it posible?

And anyhow, I've watched a video about dynamic persistent menu, it need region navigation menu, what is it for???
can anybody tell me?

I'm new to drupal.. and I don't know what to do with this module.