Setting up Afterpay

I haven't seen anything about a 2 star rating but you might mean 2 feedback rating for buyers in some categories. Alll you need to buy or sell using Afterpay is on the help page here, including the bit about needing 2 feedbacks. Easy enough to get 2 feedbacks by buying something and receiving feedback, or selling something without Afterpay, get your feedbacks, then add Afterpay.

Afterpay – Help - Trade Me