Facebook is a bit tricky when pulling in content because individual users privacy settings vary and Facebook also have a very strict API that severely limits what they share with us.
Because of that, our best suggestion is to use the Storify Chrome extension -- it'll allow you to Storify these elements directly from Facebook.
More information about that, and where to get it, is here:
Another option you have is to copy the direct URLs to content from Facebook, Twitter, etc. and paste them in the Embed URL tab in the Storify Editor. The direct URL to a piece of content is generally obtained by clicking on the time/date stamp on the post.
So, if you'd like to search for something on Facebook, you can do so directly on Facebook.com, then click on the timestamp on the post and copy the URL from your address bar. Then, in the Storify editor, switch over to the Embed URL tab and paste. The same goes for Twitter, or really any other URL source you may like to use!
If neither of those options will allow you to pull the content in, unfortunately there isn't much we can do as we are limited to what they are willing to share with us and restricted by the above privacy and API limitations.
We're always happy to help or listen, so if you have any questions or feedback, feel free to email firstname.lastname@example.org or Tweet at us (@storifyhelp).