Not sure exactly, but I think you can go to https://zapit.live

Create an account. Make sure you use your npub and not your nsec 😅. This will give you a login key and a wallet ID. Make sure you copy paste those into a note on your iPad somewhere - you will need them to log in.

Then you can log in.

Then you type the title, description. Chose something that attracts people, that want to make them buy your creation.

Then you put a URL to the digital good: for example a link to one of your songs on YouTube or on wavlake). You could also upload something to nostr.build if you want.

And your price.

Click on Monetize. This will give you a link. Put this link in a note and publish it on nostr.