From your Shopify admin, go to  Online Store  >  Themes .

2.Find your current theme (or the theme you want to edit) and then click Actions > Edit code.
3. On the left side, click the Snippets heading to access your Snippets. Once you get the list of snippets, click the Add a new snippet link.
4. Name your snippet ‘custom-attributes-review’ Click Create snippet:. Download the code and paste it in ‘custom-attributes-review’
5.Include custom-attributes-review.liquid in your product-template.liquid
                      <div id="shopify-product-reviews-zeedrop">      
                      {% render "custom-attributes-review" %}