I sell both electronic and physical copies.
Basically how it works is you have two files, a pdf of your book text and a pdf of the cover. With print-on-demand there’s no inventory. When somebody orders a copy of your book the cover and text are put together, printed and sent to the customer.
You can choose to publish only on Amazon, which may be easier and cheaper, or choose to publish on all sales locations (Amazon, B&N, Apple, etc) through printing sites like Ingramspark/LightningSource or Smashwords.
I set up my own publishing house, which means I have a company name and a Tax ID number, and my business is registered in my Town/City.
It’s not as complicated as all this sounds.
My friend published her short story through Amazon and that was fairly easy.
I’ve found this website to be invaluable for information. It’s where I got my book template.
https://www.thebookdesigner.com/
Let me know if you need more details or clarifications. Or any help. I did it all on my own (though I took a self-publishing class at a local education center) so have been through the process several times.
Do you have a cover artist?
Did your friend sell many copies on Amazon?