How to share a post on whatsapp with image included?

This WordPress website is in Hindi but it fulfills the function I seek, http://polkholpost.com/?p=807541 when a similar click on WhatsApp shares on http://jhpost.in/2018/05/28/213/ does not add the image on the page to the shared content.

Added the same plugin to verify and it does not work.

Can someone please explain what needs to be done? Thanks in advance.