There are two ways to edit attachment labels. Click “Space Tools” at the bottom of the sidebar, “Content Tools” then “Attachments.”
Alternatively, view the page with the attachment and click on the three gray dots in the page menu, then click “Attachments.”
You can see the labels for each attachment in this list, and you can add or delete labels by clicking on the edit symbol.
Watch our Video #74 of the Video Tutorial Series “Learn Atlassian Confluence” and read more about the subject on this page of Atlassian’s documentation.