In the first video here, you can see how to set up your access key step-by-step:

You can go to this page here to create your create your access key: AWS Account Login / Set Up

In this screenshot, you can see which button to click to create your access key: Access Key Button Screenshot

Don’t create you access key within the IAM console. Use the above steps instead.

If this doesn’t solve your problem:

That means you may not have signed up for your Product Advertising API.

To do this:

Step 1: Login into your Amazon Associates Account and scroll down to “Product Advertising API”
Here is a screenshot of where that is located at:Product Advertising API Screenshot

Step 2: From the Product Advertising API page, click the sign up now button and follow the prompts.
Here is a screenshot of where to find the “sign up now” button: 
“Sign up now” Button Screenshot