Left click on "Your Account" and choose "Order History" from the drop down menu.
As shown in the image below, there will be a "leave Feedback" button in the space noted. Left click on the button and a feedback box will pop up. Complete the stuff in the box and left click done (or what ever it says. I did this yesterday so I've forgotten by now

Once you leave feedback, the button will change to what you see highlighted in red in the image below.