1. Click How to Get Key on the Yelp Reviews card (it opens Yelp's Fusion authentication guide), create a Yelp Fusion app and copy the API key.
2. Fill Yelp reviews domain name with your business alias from your Yelp page URL (the part after yelp.com/biz/), and Yelp reviews API with the API key.
3. In the page editor add the Yelp Reviews module (Testimonials category) to a page; it has a text block you can edit.

When both settings are present the module fetches your latest reviews from Yelp each time the page loads (reviewer name, photo, rating, text, link) and shows them as cards. Yelp's API returns only a few most recent reviews. The card is Active when both fields are saved.