This theme comes with some system styles that you can use but you can't modified them.
But if you want, you can use one of those system styles to serve as a base of your own custom style.
To create a Custom Style you need to:
- select a System Style which you think it fits best your needs
- click the SAVES AS button
- fill up the form
- click the Okay button
After that, a Custom Style will be created, and you can change and save it as many time as you want.