This screencast covers a lot of bases. Check it out to see file attachments and full page story view in action! There are a couple ways to attach files. Drag them into an open story or press the paper clip button, and don’t forget, you can drag in multiple files at once! Click the cogwheel to download or delete the image. The same rules apply in full page story view.
There are also a few ways to view attachments, pop out to full story view, clicking on the attachment for a full page view of the single attachment. You can also view all images by flying over the speech bubble, click the “view all images” in flyover to see just the images on a separate page. This is my favorite way to view attachments because they’re large and in once continuous column which is great for walking through new UI changes.