Mega menu - styling change

I would like the styling of the menu on site B to be the same as Site A (see attached screenshots). Site B uses Mega Menu, and is Wordpress based.

Navigation items should be vertical rather than horizontal, sub menus should not overlap, font should the green colour with a light green background on hover with padding. Each white menu box should have a grey border with shadow as per site A - urls will be provided for both sites.