Michelle,
I know that if I log out and then sign in again, the little message on the top reminds me that I have feedback. But, if you are logged in, you or your customer will go up to the very top of your screen and click on Account.
Once you are in that section, on the top right of your screen it will list blue links, one of which says Purchase. Click on that. It will list your recent purchases but now with the new system, it will show the item your item bought, but now with a message saying Open For Review on ........ date. Once that date has passed, you should be provided with instructions. My latest purchase won't let me rate until Sept 6th, so I don't have more details.
It is giving the buyer about 2 weeks before being able to leave feedback.
I hope this helps and is not confusing!! Also, we as sellers do not leave feedback, but this will be helpful for your customers for your feedback. I once had a customer ask me how to give feedback on my purchase.
Eileen