iPhone 5s storage space
On your iPhone, navigate to Settings > General > Usage.

At the top of this page there will be a list of apps in order of how much space they use. You can use this to decide what to delete to make more room for your music.

You can delete apps on the home screen by holding down on them until they start to wiggle. Hit the little "x" on any app to delete it.

You can delete music by sliding it to the left in your Music app. Then hit, "Delete."