"ProPhoto" > "Customize" > "Site Settings" > "Social Media"
"ProPhoto 4" > "Customize" > "Site Settings" > "Social Media"
"Appearance" > "P3 Customize" > "Settings" > "Social Media"
This upload area lets you upload an image which Facebook will use as a thumbnail when someone links to the front page of your ProPhoto site on Facebook.
If your uploaded image does not appear in Facebook, or if it appears in the preview but disappears when actually sharing the link, re-save the image in Photoshop using “Save for Web and Devices” to make sure that you have a totally plain, web-safe image, and then re-upload.
Also, see our “Linking to Facebook” tutorial for more information on how linking to your site on Facebook works and certain requirements related to images when used for linking on Facebook.