Can't listen to iTunes music?

Ok so I got the iPhone 4S and I got a fewiTunes gift cards, and I entered the code and redeemed it. It said I had $40.00 in my account. So I searched for "gangnam style" and I got it for $1.29. Then I went to my music app and tried to listen to it. It said gangnam style was one of my songs, but it was all greyed out, and there was no play button! So I went back to the iTunes Store, and tried to buy it again, but it said I had already purchased it, but not downloaded it. How do I download it?

Download it? On Mac at least, you go to STORE from the top menu (think file, edit, etc) and then select CHECK FOR AVAILABLE DOWNLOADS. It should be similar on Windows too.

In itunes… Hit the three dots in the bottom right… And there will appear a menu and you'll see "downloads". Press it and you"ll see your purchased items

hoe it helps:]