Yup, just upload the screenshot to any of the image websites available and link to it in a post. (for instance: http://snag.gy/ )
And I realize that you are using WP SEO, but have a look at the source code of your website: the og: tags are not within the header block generated by the WP SEO plugin. I.e.: the og tags are currently *not* generated by WP SEO.
I can also see in the source that you are using the Facebook plugin, so this is the most likely source of the og tags at this moment.
I repeat: this is not a WP SEO issue, please close this topic.