Facebook pulling the wrong photos

I have been researching this on the site for a couple of hours and everyone keeps coming back to using the Facebook debugger which tells me this: “The ‘og:image’ property should be explicitly provided, even if a value can be inferred from other tags.” Unfortunately, I have no clue what that means. The featured image pulls correctly to Google+ Linked In, etc. However when I share to or paste the link directly into Facebook it gives me an option of 6-7 random pics from across my site. I just installed a new theme last weekend. Prior to that I NEVER had this issue. My theme creator said I just needed to install and activate Yoast SEO, but it was already installed so that was not the issue. All I know is I am dead i the water until I figure this out and none of the WP support posts on this subject previously seemed to have effectively resolved the problem for anyone, so PLEASE HELP! =)