Do not edit any of the theme core files directly, as all your changes will be lost, when updating the theme.
Use the Bricks child theme to add any custom code. You'll find a blank child theme within your Bricks account for download, named bricks-child.zip.
Upload this child theme like any other WordPress theme. Go to Appearance > Themes and activate Bricks Child Theme. You can add your own styles to style.css.