You place the code into your product template file.
Go to: Online Store > Themes > Actions > Edit code. Find your product template and add the code where you want it to show up on your product page.
For example, my product template is called "product-template.liquid" and is located under Sections. I want my collections list to show up under my product description, so I located the product description code in the file and placed the new code right before the </div> that ends the product description.
Hope that helps!