Adjust Volume
To change the volume of the watch, swipe to the Settings app. Tap on Device > Sounds and volume > Volume. Here you can adjust the volume separately for Ringtone, Notifications, Alarms, and other Media. Just tap on the sound you'd like to adjust and select the desired volume level.
Mute
You don't have to turn off all the sounds separately if you want to mute the watch, simply tap the "Mute sounds" slider once you're in the Sounds and volume menu to mute all noises from the watch.