Product Reviews by Shopify
Note: To use this Plugin block, you will need to already have the Product Reviews by Shopify app installed and configured on your Shopify store.
Here is where the app can be installed: https://apps.shopify.com/product-reviews
Once the app is installed and configured properly, just select the "Product Reviews by Shopify" block from the Plugins section of page blocks:
Click on the blue pencil icon or directly on the element to Edit the block:
Select the product you want the reviews widget to be used for by clicking on it and then click the Save button:
The actual reviews widget will be displayed on the page once the page has been published/updated:
Once a customer leaves a review, it will either be added to the page directly or becomes available within the Product Reviews by Shopify app's admin account for moderation (depending on your settings).