Setting purchased music from google play as ringtone?

I use Ring Droid. It let's you take just about any segment of any music/audio file and make it a ring tone. You can even assign to a contact right from the app.

From my LG Optimus G E970
 
Yep, I installed that. The problem is, the song isn't even showing up in all audio. It's as if it's not even on the phone.