In order to configure Open Graph Tags for Magento 2 Blog Post Page please go to Content >Blog > Posts and click on the post you're most interested in to start configuring.
On the blog post page find the Open Graph Metadata section.
Open Graph Metadata
1. Set the OG title. In case you haven't set it up the Meta Title will be used. If it isn't configured either Blog Post Title will be used.
2. In the OG Description set the Open Graph description of the post. Meta Description of the post will be used in case an OG description hasn't been set up. the Default Description will be used, if there are none of the descriptions configured.
3. In the OG Image set the Post Open Graph image (Facebook Image). If you haven't set it up the Default OG Image will be used.
4. Set the OG Type. In case you leave this field blank "article" type will be used by default.
Once you've finished the configurations don't forget to press the Save Config button.