Downloaded songs don't appear on iPhone

[Matthew20]

I have downloaded a song onto my computer and iphone. The song is in my downlaod folder on my computer. It is also downloaded on the music app on my phone. The song plays on from the music app and from my computer. I proceeded to activate local files and successfully added the song onto my comupter and can play it on my computer. However, when I go onto my iphone's spotify account, I can click on my playlist but the song does not even show up. Any help would be greatly appreciated.