Review pops would pull the Google My Business Link automatically when you set up the business, so you could immediately collect reviews and display them on the websites. 

However, if it's a brand new Google My Business account or it has some incorrect information and it couldn't be pulled from the automatic setup, you might see the notification like this: 

You can easily add the link manually following these steps: 

Step 1. Look up the Business on Google Search

Step 2. Click on the maps and grab the link from the browser address bar

Step 3. Then navigate to the tool called Pleper following this link: 

Step 4. Enter the link from the Google Maps into the converter then click the "Convert and Generate" button 

Step 5. Scroll down and find the CID link on the bottom of the page, then copy

Step 6. Navigate to Business - > Set up tab and paste the Google CID link into the Directory monitoring field  

Make sure the Monitoring toggle is set to "ON" position.

Step 7. Then click the Save button.