The Document Details section is where you can edit document-specific elements, like:
The post title (or headline)
The post slug (or URL)
Image file names
Image alt text
You can also edit multiple documents at the same time. This way, you can batch the amount of work you're doing and then automatically export multiple documents at a time.
To access Document Details, simply import a document and then click on the blue document title in the "Documents" column.