You can add widgets to your widget areas in exactly the same way you would for standard widget areas created with your theme, namely via the Appearance > Widgets screen in your dashboard or through the Customizer. Using the Customizer is by far the best way, though, as it allows you to see what the content looks like as you add it.
Go to your page and click on the ‘Customize’ button in the admin bar. The Customizer panel will open. Click on Widgets then select the name of your widget area. Click the ‘Add a Widget’ button.
You can now choose from all the widgets available to you. Click your selected widget and begin to edit it.