The watch only has one speaker not two and as far as I'm aware it does not support music playback. It would be pointless anyway as the speaker is not powerful or loud enough for that purpose. You need to use bluetooth headphones.
I've just tried that & selected the watch option but when I go to play it still says I need to connect Bluetooth headphones, think you need the music stored on the watch as well not just syncing from the iPhone...
I've just tried that & selected the watch option but when I go to play it still says I need to connect Bluetooth headphones, think you need the music stored on the watch as well not just syncing from the iPhone...
Using the Apple Watch as source is mainly for times when it's not connected to an iPhone. To use the Apple Watch as a source you need to have the music you want saved locally to the watch as well as have bluetooth speakers/headphones connected to the watch.