Post a video of your game running with your own custom gameplay music track.
Record your music track and gameplay using QuickTime and post your video onto YouTube.
Video - YouTube
QuickTime can only record the audio from a real device, you can't capture the audio with a screen recording.
Record your iPhone/iPad via USB lightning cable (plug it into your computer)
- QuickTime > File > New Movie Recording > Choose your iPhone
Audio - SoundCloud
Upload your audio file to SoundCloud.com to share a link to the music.