Logging in to Amazon Prime Video when I have subscription through Apple

I have a valid subscription to Amazon Prime Video, which I added on my Apple TV. I am also able to watch content on the Prime Video app on my iPhone.

Due to constant power cuts in my country, I need to watch content on my MacBook. Both the Prime Video app i have downloaded onto my MacBook, and a web browser, require Amazon Prime Video login details. What are my log in details when I have purchased my subscription through Apple?

If I try use my email address associated with my AppleID I am prompted to sign up again, or start a trial, as I had previous subscription using that email address.

How do I log in as a subscriber through Apple?

Edit:

Shortly after I posted this question I started watching some content on my iPhone in the app, and then a second Prime Video app icon appeared in my Dock, alongside the already running app icon, but with a small phone icon added to it. As soon as I clicked on it my MacBooks Prime Video app was automatically logged in to my account.

But the question still remains, how would I log in if I wanted to watch through a web browser?