To use the category index page template, create a new page (Pages > Add New) and find the Page Attributes tab in the right sidebar.
Choose Category Index Page from the Template dropdown menu.
Next, go to Appearance > Customize > Widgets > Category Index and set up the Flexible Posts widgets however you’d like.
See the Homepage setup instructions for more info on how to set up Flexible Posts Widgets.
If you don’t see the Category Index widget area in the Customizer, you’ll need to go to Appearance > Widgets to add your widgets. Or you can go to view your Category Index page (for example: https://demo.studiogem.co/foodie/category-index/) and select Customize from the admin bar. The widget area will be displayed when the page is the active page in the Customizer.