To successfully allow a visitor to share AV items (Series, Authors, Categories, items, etc.) , the item must have a Friendly URL defined and set the Title and Image meta tags.  The meta image that you upload will be the image that is shared on social media when a visitior to your site clicks the Share icon on the item.

Please note: the Additional Meta Tags field on a blog post is an optional field for meta tags that don't fit the other meta tag fields above it.  It must be a fully coded meta tag. If in question, leave it blank.

Check facebook developer tools if you are having difficulty sharing items. There are recommended and minimum requirements for image sizes.

If you are having issues sharing your AV items, you can run the facebook sharing debugger for insights.