How to add site description that shows up when posting the url to Facebook

Thank you for creating this theme. I’ve used it for http://www.chepetto.nl.
Now, when we want to share the link on Facebook, the description area stays empty. I’ve added WordPress SEO by Yoast and tried All in one SEO (both deactivated now), but still no description shows up. I’ve also added meta description code to the header.php, but that doesn’t seem to work either.

Anyone any idea’s on how to fix this? Thank you!