Hello again!
I’m glad you’ve found an easy way out ?? I’m happy you like the plugin, too!
If the featured image is displayed on the page, then Google will have no trouble finding and indexing it.
Otherwise, I’m not aware of any methods that allow Google to index and use it. Displaying (featured) images next to pages on the SERP is rare, and often only reserved for Google News publishers’ articles.
If you’re dealing with local business, you can sign up for Google My Business, and have a (non-offensive) image of choice displayed in the Knowledge Card on the right. The display of which is only reserved for location-based and nearby searches, however.