The Amazon internship process is pretty short compared to other companies. This is what it looks like:
1. OA 1: Two coding problems to be solved in 70 minutes. You can't really prepare that much for them, but I would recommend checking out the Leetcode discuss forum. The questions were quite easy.
2. OA 2: This is a workplace simulation and workstyle assessment. The workplace simulation gives you a bunch of situations and a number of responses and you'll have to rate the responses by effectiveness. I'd recommend reading the Amazon Leadership principles page. Deadlines and customer satisfaction are the most important factors so always rate the option that maximizes either the highest. The workstyle assessment just asks you some personality questions so there is no real way to prepare for it.
3. Final interview: This is the last step of the interview process. You'll have a virtual interview that will last ~45 mins with an engineer from Amazon. They will ask a few behavioural questions based on the leadership principles and then ask you 1-2 leetcode-style questions. Prepare some relevant stories from your life and make sure to highlight the leadership principles in your answer.