How to add a featured Case Study page to a Product page?

I want to add the Case Study webpage of https://guardianchem.com/articles/case-study/how-safeguard-al-safely-cleans-aluminum/ to a product page https://guardianchem.com/product/safeguard-al.

I tried different ways but none of them worked.

Could anyone know how to do it?

Thanks in advance!

The page I need help with: [log in to see the link]