Homepage Image

www.with-a-grain-of-salt.com AHHHHHHH! I have spent five hours total trying to figure out how to link a specific image to my homepage so that when I share my site on social media this specific image shows up. Right now, if i try to post my site on FB, the title comes up with a box for an image but it's empty. I know how to make a featured image for posts and pages and I also know how to make sure that the image I want is scraped but how do I do this for my homepage/overall site??? Help please!