To get ready for this recipe, take a look at the drop-down component documentation available at https://v4-alpha.getbootstrap.com/components/dropdowns/. Also, refer to the navbar component documentation at https://v4-alpha.getbootstrap.com/components/navbar/. Finally, visit the address for Yamm3 (yet another megamenu for Bootstrap 3), at https://github.com/geedmo/yamm3.
bower install yamm3 --save