Drop down sub menus

I have a theme and a child theme that I am working on, in localhost on my laptop. I have added menus (main pages) to the menu bar and would like the sub pages to show as drop-down menus.
(other themes I have used just did this), so is there something I should have checked or activated.?
The child theme is one that I purchased, though support has been very good up to this point, I don’t seem to be getting an answer on this..