If you're running iOS 7 on your iPhone or iPad, iTunes Radio comes bundled right in the Music app. While you can always listen to the stations Apple is currently featuring, you can also create your own based on any genre, album, or track you'd like.
- Launch the Music app from the Home screen of your iPhone or iPad running iOS 7.
- Tap on the iTunes Radio tab in the bottom navigation if you aren't there already.
- Scroll down a bit and tap on the plus sign on the block labeled New Station.
- Here you can search for an artist, pick a genre, or look for a particular song.
- Tap on the result you'd like to create a station based on.
That's all there is to it. iTunes Radio will automatically start playing songs based on your criteria. The station will also appear under your My Stations section so you can always go back and listen to that station again whenever you'd like without creating it again.