With the help of Gecko Customizer settings, you can customize the font used on your site. You can find these settings in WP Admin -> Gecko -> Gecko Customizer -> Site -> Fonts.

Choose the font you want to use on the site from the Google fonts available in the list.

You can also change the font size and line-height using the settings available in WP Admin -> Gecko -> Gecko Customizer -> Site -> Typography.

To customize global headings and text color, go to: WP Admin -> Gecko -> Gecko Customizer -> Global Colors -> Typography Colors.