This articles explains how to quickly enable the Hey Siri feature of your Apple Watch.
Access your applications by pressing the digital crown shown on the Watch Face. Select the grey cog icon to navigate to your Settings option, and click on Siri. Toggle on the Hey Siri option to enable the capability.
Once activated, the Hey Siri function allows Apple Watch users to ask questions, send messages, and even make calls, by simply raising their wrists and saying, "Hey Siri" into their Apple Watch.
Siri is a simple way to navigate the Apple Watch and access its many features.