create a new download after submitting a (gravity) form

The frontend uploader is to extensive for my users and they should not see all the options that are available. My users only need to upload new files / packages (in addition with some custom fields…)
So I have a created a gravity form where they can upload the files, title & description and with wp_insert_post I created a new download package… but I need to add the files from the upload to the download-package?

Anyone knows how to solve this problem?