With the help of =ProF=, I can now say what goes in the fields:
szLink - the full link to the site supporting your app (e.g. "http://www.yourapp.com")
szPicture - the full link to the image to be displayed within the post (e.g. "http://www.yourapp.com/fbstuff/fbimage.png")
szName - the name of your app, which will be displayed in bold above whatever is in szDescription, both will be to the right of the image in szPicture (e.g. "Your App Name!")
szCaption - something that gets displayed (converted all to caps) below szDescription (at the very bottom edge of the image)
szDescription - some text to display (e.g. "Welcome back to the app <user name>")
Cheers,
Ancient Lady
AGK Community Tester and AppGameKit Master