Pay Pal issue connecting to digital file

Please help!

I am a musician and I would like to be able to sell my digital files through paypal on my website. I have managed to install the plug in and have figured out how to add a paypal button but I’m unsure how this links to the actual track that you’re selling? In other words, the paypal button shows up but there is no actual file to download? What am I doing wrong..

Thanks so much!

https://wordpress.org/plugins/wp-ecommerce-paypal/