Simple file upload from non-box user

After I share a link to my folder with any third party, I want to allow them to UPLOAD anonymously using a simple drag-and-drop or copy-paste method.  How do I do that?  And Ideally, I want that third party person to only see their own file and not the file from any other user who did the same thing.  Or, if not possible, then prevent one user from downloading a file uploaded by any other user.

Specifically, I am asking Concerto Competition applicants to upload their audition audio recording to a common UPLOAD Folder such that only I can see the files uploaded by all applicants.