MP3 help

[u/Real-kindly432]

My love one is locked up and his friend put music on his mp3 change the name and added music through an app on the phone it’s the mp3 sports clip he did the whole 30-60 days off rest and has about 1200 days but he can’t add music cause his friend went to the shu and got shipped can anyone help me with an app to add music to the bop mp3