The Design options are available under the Design Tab of Template Options. Here, you can set the font, colors, different page layouts, and add your custom css code.
Google Font: Select the font for the website.
Primary Color: Set the primary color (RGB) for the website.
Secondary Color: Set the secondary color for ther website.
Registration Layout: Select the layout for Joomla registration page.
User Profile Edit Layout: Select the layout for the Joomla user profile.
Custom CSS: Here, you can add your custom style.