i was having this problem as well but i figured it out, when you hook up you're iphone 5 to you're computer on the left side you're device should pop up with the name (example: Alexis's Iphone) click on that, then on the top it will say all different things you can click on, go to the place where it either says "music" or "sync" and then on the bottom all different colors should pop up where it shows how much space you have used so far, then on the right hand side of that bar it says sync, after you have created/bought new music on you're library you simply click on that button and it should most likely work, thats what i did. Hope i helped (: