You're only allowed CSS and HTML. Put the HTML in the "About Me" section and the CSS is any of the other sections. If it's a really customized (lots of overlapping divs) and you put the HTML and CSS together, it'll cover up the "submit" button. Always use "safe mode."
There are lots of premade layouts out there, but it's best to do it yourself if you have the time / patience. They've taken out a lot of markup so you have to do everything a long roundabout way.
I highly recommend downloading the
CSS stylesheet they use for their site so you can know which classes are already defined.