GoPRO Quick App with IpHone what is the best quality wayy add your own songs or records ?

I am trying use go pro quick app to edit videos and pictures and i love it super easy to use best quality and effect but gopro app music section just let me use when they have basic tunes i try to add music my phone dont let me to download and use iwant to add music also same app as a gopro because i try add song other apps they kill the video quality help please anyone here its my first question.thanks