Change menu font

Hi,
I’m a total newbie to the amount of alterations to the theme that I’m needing to do to set up my brother’s site (conforming to corporate branding). By using Easy Google Fonts Plug-in and custom font controls I have managed to adjust pretty much every font on the site except for the links in the primary menu. I can’t seem to figure out the CSS selector to use to create the right font control to adjust these.

Side Note, I essentially need the entire site to all be Nunito Sans… if there’s an easier way to globally – please let me know!

PS – please use newbie-friendly language in any replies!

The page I need help with: [log in to see the link]