If you’re talking about a scrolling marquee style banner, simple banner has multiple CSS fields that allow you to make your banner look and act however you want. There are many search results online for marquee text that can help you achieve this styling. However, I always caution people against using a marquee style banner. Marquee text provides a unfavorable experience for accessibility, e.g. users who need to use screen readers or other accessibility mechanisms. Modern UX also suggests that you should never hide information that you want the user to see, and a marquee style banner will hide portions of your banner text consistently.
If you are talking about the banner while a user scrolls down your site, the .simple-banner-scrolling CSS box is where you want to put all of your styles. After a user scrolls past the banner that .simple-banner-scrolling class is applied to the banner, allowing you to adjust the styles of the banner after the user has scrolled past the initial version.