The following steps to configure social sharing links in Magento 2 Blog 

  1. Go to Stores > Configuration > Magefan Extensions > Blog and find the Social section.
  2. Enable AddThis in order to display social sharing buttons on the storefront.
  3. Enter the AddThis ID. In order to learn where to get the AddThis ID follow the link.
  4. Set the AddThis Language. ( it has to be two-character e.g. en, fr, de, nr )

Magento 2 blog social configuration

Once you fill in all the corresponding fields and Save Config, you'll see the social sharing links on your blog posts.

Magento 2 blog demo