If you have previously bought music on another device, you don't need to buy it again: Go to the app. Tap More (...) and then Purchased .
: You can add millions of songs to your library and download them for offline listening without buying them individually. Important Notes for iPhone 6 Users
: Ensure you are signed in under Settings > [Your Name] > Media & Purchases (or iTunes & App Store on older iOS versions).
If you prefer streaming over owning individual files, the app on iPhone 6 supports Apple Music (provided you are running iOS 8.4 or later). Cost : Requires a monthly subscription fee.
: Look for the purple icon with a white star.