If you go to the left hand side where my name shows, you will see a trade rating number. If you click on that, it will take you to the feedback page. You should then see a link "submit feedback", click on that then the rest should be straight forward.
Let me know if you need any other help.

Hi nika im trying to leave a trade rating for you but i don't know where to do this? can you direct me to the proper place, thanks

Thanks for the trade, I sent mine out to you that afternoon, hope its all right, i haven't traded before.