Changing Height of Banner

I have the banner set to slider images, but I’d like to change the resolution of said banner. I’ve tried finding it in the code to change the size to no avail. I believe it is the <div id=”banner” class=”cactus-section cactus-section-banner”> that I want to change the size of, so it changes the size of all of the banner images.

Is there a way to add custom CSS in order to make these changes?

Any help would be appreciated.