The examples in guide is based on Shopifys own Product Reviews app, but you should be able to use any other app of your choice.
See Shopify's Product Reviews app on the App Store
When you have installed the Products Review app, you will need to embed some code in Posterly for it to work. In order to do so, you will need to paste the following line of code into the description or footer field of a design.
<div id="shopify-product-reviews" data-id="{{all_products['{{SHOPIFY_HANDLE}}'].id}}">{{ product.metafields.spr.reviews }}</div>
Below you see an example where the code snippet has been copy/pasted into the footer field of a design in the Design Studio part of Posterly.
For other apps than Shopifys reviews app, you will need the following code, to replace the product ID line of their code snippets.
{{all_products['{{SHOPIFY_HANDLE}}'].id}}