How to get free music on iTunes?

I have an app that downloads music but it's just music on that app, and not in 'my music' on my iPhone. I only have one song cause I'm only a teen and can't afford songs really. The reason I want songs is because I want to make a music video on videostar.

You can take any mp3 file (or rip CD's to mp3 files) and just add them into itunes, then add to ipod or phone.