But, Some of the themes are just so simple to customize and one of them is GeneratePress. GeneratePress is a lightweight and simple theme and my third favorite theme after Genesis and Beans.
Every theme comes with their own settings and customizations options. However, themes like Genesis are so easy to configure and customize.
The basic options of a theme can be found here Appearance >> Customize and from here you can add, edit and delete the stuff individually.
GeneratePress contains most of their settings in default customizer and more options can be found here Appearance >> GeneratePress.
Every theme has their own menu positions so you need to check where it is placed after activating.
To know more about Menu position, read https://developer.wordpress.org/reference/functions/add_menu_page/