How to get a cloud next to your iPhone songs?

My friend has an iPhone, next to a few of her songs in the music app is a cloud icon with an arrow pointing downwards. The song is then only available to play when she's online!

I would like to know how to do this? Does anyone know how?

The cloud means that she has iCloud enabled which you can do in the settings on your iPhone. The cloud will only show up next to songs that you brought in iTunes.