WordPress widgets allow you to add additional content and features in your sidebar or other places on your site very easily without writing any code. Widgets were originally designed to provide a simple and easy-to-use way of giving design and structure control of the WordPress Theme to the user.
To manage your widgets go to Appearance > Widgets
See below picture for reference.
From there, you’ll see the available widgets and also your inactive widgets. To add widgets to the sidebar simply drag and drop them to your sidebar. You can configure your widget with your choice of settings. Make sure to click the save button for each individual widget.
Most WordPress themes are not required to have a widget area, so if you do not see any widget areas, then it means that your theme does not support widgets. Most WordPress plugins often add their own widgets as well.