Please visit Mass File Upload: User Guide to view the user guide.
This user guide will walk you through the required steps to use the Mass File Upload.
PS: View Mass File Upload Salesforce file upload app on Salesforce AppExchange:
https://appexchange.salesforce.com/appxListingDetail?listingId=82cf236b-1ee8-4ea7-aebf-fd0c89fb93bd