You can configure the widgets from either of the following locations:
Dashboard >> Appearance >> Customize >> Widgets. or
Dashboard >> Appearance >> Widgets.

Here we are exploring the first option:
Here widgets will display according to the page you are currently viewing you will see the following message:
“Your theme has 6 other widget areas, but this particular page doesn’t display them. You can navigate to other pages on your site while using the Customizer to view and edit the widgets displayed on those pages”.
Now you can add your desired widgets at a particular location by “Add new widgets” option.