You can capture the screen on your Apple Watch using the Digital Crown and the side button.
How to turn on the screenshot setting.
1. On your iPhone, open the Apple Watch app.
2. Tap the My Watch tab, then tap General.
3. Scroll down, then turn on Enable Screenshots.
How to take a screenshot.
1. With two fingers, press the Digital Crown and the side button at the same time. The screen flashes when you take a screenshot.
2. To find your screenshot, go to the Photos app on your iPhone, tap the Albums tab, then tap Screenshots.
IPhone And IPad Apps for the Blind And Visually Impaired 