When you use the upload file server behaviors, a new binding group is greated in the bindings panel:
WA Uploaded File (File Field name)
where File Field name is the name of the file field.
this binding group contains the Server File Name biding which contains the name of the uplaoded file.
you need to use the Data Assist insert record behavior to insert the new record, and bind the file name column to the Server File Name binding.
see this tutorial for details: