Go to https://shopify.com/admin/online_store/preferences to update your social sharing image and meta data.
I would add that you should test in multiple places - from the facebook comment section (as you posted) to sharing a post, to facebook messenger and WhatsApp and even LinkedIn (or whatever the popular platforms are for your target audience).
As you are testing you may find that you want to change the image. To do that easily use the Facebook Sharing Debugger (which will help you refresh any cached images)
There's also the twitter card validator: https://cards-dev.twitter.com/validator
and the Linkedin post inspector: https://www.linkedin.com/post-inspector/
Im sure there are other validators for other