Galaxy Core prime- SM-G360G - RECORDING MUSIC INTO GOOGLE PLAY MUSIC

[AC Question]

I am attempting to copy music files from my windows pc to the above phone.
I have copied them via the USB cable into the music file on the phone (as per google's instructions) - All the files show in the phone. But, do not display or play in Google play music. I have logged in and out of my google account.
Where to now??
I'm I copying them into the correct music file?
Cheers,
John.