Hi Cindy,
All articles are available for sharing if social sharing is enabled for the application. Don't forget: people who have names on the credits page might want to share it so their mom can see
We don't currently support customizing the content of the social share landing page other than specifying some article text. You can, however, point the share URL to a totally different page on an article-by-article basis. This is useful if, for example, you have a website that's already hosting equivalent content. This value is set on the Social Sharing tab of article properties, change the Social Share URL to point to your custom page.
Neil