To watch anime on Amazon Prime, you need to have an Amazon Prime subscription, which costs $12.99 per month or $119 per year. You can also sign up for a free 30-day trial if you're a new user.
Once you have an Amazon Prime account, you can access the anime section on the Amazon Prime Video app or website, and browse through the available titles. You can also use the search function to find specific anime that you're looking for.