Widgets are items that can appear in different places across your site such as in the sidebars and footer. An example of a widget is Recent Posts. Using a Recent Posts widget could display a list of your most recent posts in your site’s sidebar. Your options for widget areas are dictated by your theme, so if you want a widget in the footer, but your theme does not give you the option, consider moving the widget or choosing a new theme.
For further instructions see link.
Content taken from University of Mary Washington