You can change the entire look & feel of your site by adding custom CSS and/or HTML to your website. Be aware that added code affects your whole site. Note that mono does not support custom-added CSS or HTML.
1) Adding CSS: Click on the 'Custom CSS' tab under site settings and apply your CSS into the editor. Press 'save'.
2) Adding HTML: Click on the 'Global HTML tags' tab under site settings and apply your HTML-code into the editor in either the header or the body field. (Google analytics script must be applied in the header). Press 'save'.
Remember to publish your site after changing a site setting in order for the changes to take effect.