This widget comes free with WPmozo Addons Lite. To use it, simply install and activate the free version of plugin.

https://wordpress.org/plugins/wpmozo-addons-lite-for-elementor

How to add widget on page

The Facebook Comment widget allows you to easily embed Facebook’s commenting system on your website, enabling users to leave comments using their Facebook profiles and helping boost engagement and social interaction directly on your pages.

To add the Facebook Comment widget, follow these steps.

1. Create/edit a page/post that uses Elementor builder.
2. Create/edit container.
3. Search widget WPMozo Facebook Comment under WPMozo.