If you have one product that can be distributed as a digital good (like e-books, mp3 files, movies, etc) you have to follow this guide:

1- Zip the files and copy them into digitalGoods folder

2- Edit each individual product using the BackOffice and enter the file name into digitalGoods field

3- Consider that orders should be marked as PAID or DELIVERED to enable the customer download so configure your online payment gateway Silent Response or manually mark orders as paid from BackOffice when you confirm the payments

4- Your customers may download purchased files from Customer Menu, order Tracking. The files will be renamed in real time with OrderNumber_FileName.zip (like Order2008_File8.zip) and the Browser will show a download popup box.

5- You can include a custom message in the outbound email with payment confirmation so your customers will know where to go in order to obtain the purchased files.