Many of the solutions above don’t work, or are very outdated and misleading. There are lots of recent high quality products that work with Facebook. For example, you can check out this online demo to feel the difference in comparison with the old widgets: https://elfsight.com/facebook-feed-widget/ .
The installation of any widget consists of the following points:
Confugre a Facebook Feed for yourwebsite;
Get the code;
Install the code to a page or to thewebsite’s theme.
Find out more in this tutorial: https://elfsight.com/help/how-to-add-facebook-feed-to-squarespace/ (it’s a tutorial specifically for Squarespace websites).