In order to display star ratings for each product, you need to be using the Kudobuzz review form widget for product reviews.
If you do not have this installed yet, kindly follow this tutorial.
1. Copy the following code :
|<span class="rateit k_product_rating" id="%%GLOBAL_ProductId%%"></span>|
2. From your Bigcommerce admin, click on Settings >> Design
3. Click on Edit HTML/CSS
4. Using Command/CTRL + F, search for productdetails. Click on ProductDetails.html and paste the code under the price section.