Go to the Customizer -> Footer Settings.
The footer template that is best to select for adding widgets is Widgets Boxes Template. But you can also add widgets to the Footer 7 Template, or to the Footer 4 Template.
To insert widgets in the widgets boxes, go to the WordPress Admin dashboard -> Appearance -> Widgets.
Simply drag and drop widgets from the list of available widgets, to the Footer First Box/Second Box/Third Box Widgets sections.
