Can I transfer youtube song to Apple Music
I'm trying to transfer a specific musical arrangement from YouTube to iPhone imusic
You would need to to download it from youtube first, something we cannot discuss here as it breaks many copyright and youtube regulations to do so, then once downloaded import it into iTunes, and finally sync it to the iPhone.
Once its downloaded you can follow these support documents to add it to iTunes, and sync it to the iPhone.
iTunes for Windows: Import music and video already on your computer
iTunes for Mac: Import music and video already on your computer
Sync your iPhone, iPad, or iPod touch with iTunes on your computer using USB - Apple Support