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:

  1. select a System Style which you think it fits best your needs
  2. click the SAVES AS button
  3. fill up the form
  4. 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.

Selecting a System Style which fits best my needs
After clicking the SAVE AS button, fill up the form
After clicking the Okay button, a Custom Style was created, and now I can change this style as many time as I want