How do I increase height of words in header menu? (the menu with contacts, home)

my website is https://www.iamdentistry.com … My menu bar that has Home, contacts etc. Im guessing this is called the header menu? If you look at the site the bottom words are cut off a little. Where do I go and what line of code do I look for to increase the height a little bit (the height or distance, im not sure what to look for) so the words on the menu can look normal and not cut off by its design?

Thank you

(im guessing I go somewhere in the editor?)

I also have a custom css, do I put something in there?