Some WordPress themes come with Option Panel in the backend. Some WordPress themes use Live Customizer. They both helps you to customize your site.
The Fox comes with Live Customizer. You can find it by navigating to Dashboard > Appearance > Customize, or hit the “Customize” button on menu bar.
Search for option
The Fox is among rare themes that includes option search functionality. This is not a built-in feature of WordPress. You can quickly search for your desired option in the Customize panel.