You can sync playlists and albums on your Apple Watch using watch OS 4. You can keep one music playlist on your Apple Watch at a time. Audiobooks and podcasts aren't compatible.
- On your iPhone, go to the Music app.
- Tap the Library tab, then tap Playlists > New Playlist.
- Give your playlist a name.
- Search or tap to find songs, artists, or albums to add.
- When you find something that you want to add, tap the “+” sign.
- After you add the item, tap Done. You can then search for more music to add.
- When you're done adding music, tap Done to save your playlist.