It's pretty much all CSS. So, you need to know a bit about CSS. If you have a basic understand of CSS using the style editor is fairly easy. Even if you don't have much CSS knowledge, if you just make a copy of the default style, from within the style editor, and play around with it, it's pretty easy to get the hang of. With the copy you can change some of the various properties and get an idea of what they do.
You can also try importing some from our Style Download forum to see examples on how various settings look.
