Cover
Click the cover placeholder at the top of a Doc to choose an image. More then offers View Attachment and Download Attachment when a cover is set.
Media tab
Open Media and choose Upload File. Search with Search media. An empty tab shows No media yet.
In Notes
Insert a media layout item from Add, then attach a file to that item. Display can be Wide, Full, or Card.
Comments
The comment composer has a paperclip to attach a file to a comment.
