If you want to modify the theme beyond the giving options, you'll have to modify the theme files. But if you do this directly by editing a file, all the changes will be lost when the theme will be updated and the file overwritten.
Use and edit a child theme instead. By using a child theme you will ensure that your modifications are preserved.
We prepared the child theme for you. It is included in the main theme package.
Using a child theme requires some WordPress development experience.