See where under your username it says "itrader: 0/0"?
Go to his username and click on the first number (boldfaced 0 under your name). That takes you to the itrader screen for that guy and you can click on where it says "submit feedback for XXX". He must do the same for you.
You mean a trade as opposed to a purchase for cash? Yeah, same difference. It's a financial transaction meaning it involved each of you giving something of value, be it cash, goods, or services. In your comments you might indicate it was a trade (like "thanks for the quick shipment and problem-free trade for my cue"). No biggie.