I cannot play the songs I renamed, it just says its is unavailable.

And how do you "copy it to this device"?

Appears:

"Not Available On This Device

This song on your other device doesn't match anything in the cloud, so we can't stream it for you here. To play this song, copy it to this device."

make sure that you have renamed it correctly. If you haven't reanmed with correct extension/filetype (say mp3 or mp4) it will not appear.   Also try reopening  the app and see if it appears it might require a refresh or something.