If the selected Salesforce object type supports it, and if it is a Push action, you will be able to specify any file attachments that should be synced. File attachments are synced separately from the fields themselves, and the newly created Attachment object in Salesforce will be linked to the created record.
In order to push an attachment to Salesforce
You won’t be able to see your attachments in Salesforce until you enable the Notes and Attachments panel. Additionally, an attachment being edited will NOT activate a SF action in any case (created, edited or submitted). The upload task will need to be marked as Complete.