Header Image covered by Menu

Having looked on the forums for help with most of the issues we wanted to address for how our site should look, I was unable to find anything about one of the problems we have.

Namely, the sticky navigation menu is covering up the header image, which in turn causes too much empty space between it and the start of our content.

Mainly, I am hoping someone knows some CSS coding I can use to move the sticky menu farther down the page so it doesn’t cover the header image. Or where to find the code that controls the location of the menu.