If you want to include more than one file in your product, you’ll need to put all of the files in one folder and list the folder as your product file.
If the files you want to list are Google Apps files (Google Docs™, Google Forms™, Google Sheets™, Google Slides™), put all of the files into one Google Drive folder and list the Drive folder as your product file here. You can also include PDF files in Drive folders as needed.
For all other file types, put all of the files into one folder and then compress the folder into a ZIP file. Please be sure the title of the files and folder include only alphanumeric characters, and do not include any special characters listed here. Then, upload this ZIP file as your product file here.
How to create a ZIP file on a Mac:
How to create a ZIP file on a PC: