This feature has been deprecated, and will be removed in a future release of Appian.
You will no longer be able to attach files or notes to tasks or running process instances.
Files can be uploaded with the file upload component and managed with Appian's Folder and Document Management system.
Store comments as a field in a data store so they are part of the record you are working with.
For information about Adding an Attachment or a Note to a Task [Deprecated], see the Appian 16.2 documentation.