1. Enable LINK in Image > Image Attributes
2. Change text for link in your language file to say something like 'post to facebook'
3. Set Image>Click=link
4. Add custom links for each image like this one:
http://www.facebook.com/share.php?u=htt ... oto001.jpg
Actually this feature is not exactly made to that because it does not support templates, you can't have automatic links for all images, so you have to change them manually.
Or you can edit folderdata.xml with some text editor to inject links for each image.
But again, while this feature MIGHT be used for what you want to achieve and it WILL be working fine, it's not the best in usability.