To play Apple Music on your Apple Watch, follow these steps:

1. First, make sure that your Apple Watch is connected to your iPhone and that you are signed in to your Apple Music account on your iPhone.
2. Open the Music app on your Apple Watch. You can do this by tapping the Music icon on the home screen, or by using Siri to launch the app.
3. Use the digital crown or your finger to scroll through your music library or playlists. You can also use Siri to play a specific song or artist.
4. Tap on the song or playlist that you want to play to start listening.
5. You can control playback using the playback controls on the screen. You can pause, skip forward or backward, and adjust the volume.

Note that you will need an active Apple Music subscription to play music on your Apple Watch. Also, keep in mind that playing music on your watch without your iPhone nearby will require an Apple Watch Series 3 or later with cellular capability.