There are three options that can be used in combination to enhance your sites appearance. These options are accessible by clicking on the "Change Appearance of Your Site" icon on the Dashboard. (Dashboard is accessible through the navigation bar of the Site Builder)

After clicking on this icon you will be taken to a page where you can:

Choose a site design

Here you can choose one of three styles that best suit your site functionality and look.

Choose a color scheme

Here you can further enhance you site style by choosing a color scheme that compliments your site and artwork.

Create your site header

Here you will be able to customize the information on your site header.

Once you've made your customizations, you will then be able to save and publish your site, as well as having the ability to further customize your site whenever you should need to.