Navigate to your website admin, browse to Appearance > Customize > Widgets > Select a Widget Area > Add a Widget.
At the left side, you will see the list of widgets available for you to use.
When you click on any widget, it will be active on the Widget Area of your choice. You will get an options screen, where you will be able to see all the available widget settings.
Lets add the About Me Widget as an example.
All changes have a live preview. Click the Publish button to have the change appear on the live website.