Within your dashboard of WordPress, when you begin a new post/page OR edit an existing post or page, if you scroll down a bit, you'll see the All-in-One settings area (below when you put in your content)

It will appear like this:

These are the general settings for the post or page where you can add the Title and Description. But, I circled another setting "Social Settings' tab.

Click that tab.

The following will appear:

Sidebar NOTE:

You can actually specify on the previous tab what you want the title and description to been seen as to the search engines and then within this tab, type in a different title and description for social sharing. I usually just copy and paste from the previous tab, but it CAN be different.

Okay, so.... take note of the images that All-in-One sensed from within the post in the image above. BUT, I have often tried to select one of these, but it still didn't share the image. So, I began to use the Custom Image option shown in more detail here:

This seems to specify the image in a different and more unique method. Also, I set the exact measurements (Width and Height) to avoid any distortion with the social sharing.

So, lastly, I update my blog page or post with these settings.

NOW, when I share, it turns out more like this:

AS YOU CAN See..... this is MUCH more professional and enticing than the silhouette guy or no image at all.