To track commissions on multiple websites, there's two steps:
Go to your Your Associates Account settings and add additional websites to the list of Your Websites.
Amazon doesn't explicitly support creating different URLs for different websites.
Rather, you will need to create unique Tracking IDs which both encompass the information about which website the sale came from and which piece of content it was.
For example, using this pattern:
Which results in a combined tracking ID such as:
Then, you'll want to create Label Rules in order to connect incoming sales to websites and pages in Affilimate.