You do not need to add the affiliate details each time you create a new project or site.
Any affiliate details you enter are instantly available across every project and Web site in your system, which means that you only need to enter the details once.
This means that you can earn commissions from multiple sites without having to sign-up for the affiliate scheme each time. Some affiliates schemes do insist that you only use the affiliate details on the site that you have signed up for, but these are few and far between. Most affiliates are happy to pay you the commission no matter where you put the link.