Google search Amazon Affiliates and it will take you there. I believe it's free to become an affiliate.
If you are just beginning, there are also many other programs to choose from. I've got a list at my website. Just check them one by one and study what they offer.
There are many Amazon online guides available. I think before posting these kind of questions, you should search over the internet about it.
I agree but having said that...researching on the internet as a beginner becomes overwhelming. If you do not even understand basic terms related to this field, you are stuck right away. It's been 2 weeks researching Amazon Affiliates, how to get a domain, what is hosting exactly...and every site leads you to someone else's 'best' or 'fastest' way to earn. For a true beginner, it's about Step 1..., Step 2...we are talking Internet Marketing very 101. I have 3 strong niches(I learned about that word), not a good writer but determined to accomplish my goal.