By default Facebook and other sharing platforms will grab the most accessible image on a page unless you have a specific share image applied. You can set this share image for each page of your site.
Setting the Share Image
Select your page and go to the SEO Settings in the right sidebar.
Find the Share Image setting and click to Choose Image...
3. Select your image (or upload and select)
4. Publish to make the change live
The share image for Blog templates is set inside Wordpress rather than in the Showit editor.
1. Login to the Wordpress admin and select Edit on the Page you are sharing:
2. Set the Featured Image on the page:
3. Click Update in the top right panel to update the page.
Clear Facebook Cache
Facebook cache's page information for a period of time. If you'd like to force Facebook to refresh it's cache you can follow these steps.
Visit the Facebook Batch Invalidator Tool
Paste in each page's URL that you'd like to reset the cache for.
Once it's reset new posts will pull the new share images you have set.