You must use both a unique public key/private key pair (each key pair, an “Account Identifier”) and an Associates tag parameter (which can be either the Associate ID issued to you under the Amazon Associates Program or a related Associates Program tracking ID) to identify your account and make calls to PA API. You may obtain your Account Identifiers through PA API account creation process.
When you have your own product or service you hold a lot more control of the funnel from beginning to end. But I’ve worked with many marketers to help them better control the best affiliate marketing funnel with banner ads, blog posts and social media. Once people move from those elements to the sales page – I help them control their message and email marketing campaigns and everything behind the scenes.