Taking a screenshot of your Android Wear watchface is a convenient way to show off your new gadget. Unfortunately, taking a screenshot on an Android Wear device isn't all that convenient. In fact, you can't take a screenshot on your watch without connecting it to a computer and using a the command line to capture and export the screenshot.
If you're at all familiar with using an Android device and ADB commands, you likely already know how this will all play out. But for those who aren't familiar, you will need to download and install the SDK tools and proper drivers for your device. You can get started by visiting the Android Developer site, where you'll find the Android SDK and developer tools.
After installing the Android SDK, but before attempting to take a screenshot of your Android Wear device, you'll need to enable Developer Mode on your watch. You can do this by going into Settings, followed by About, and tapping on the Build Number a total of seven times or until you see a prompt letting you know you're a developer. A new "Developer options" will then show up just below the About listing in Settings (as seen above).
From here, connect your watch to your computer via USB and enter a few ADB commands. Remember Mac users, you'll need to add "./" (without the quotes) before a command.
To take a screenshot:
adb shell screencap -p /sdcard/screenshot.png
Then to transfer the screenshot to your computer:
adb pull /sdcard/screenshot.png
The entire ADB process can be intimidating and confusing, but don't feel bad. Everyone has to start somewhere. Personally, I started with this guide on Android Central to get up and running. If you run into issues getting it setup, be sure to read through the page I just linked to. It's thorough yet easy to read, which helps to get newbies started without feeling like you're being talked down to.