The what3words app widget is only available for iOS devices,

For iPhones operating on iOS 14, touch and hold anywhere on the screen until the apps jiggle. Tap the plus sign in the top corner of your screen and scroll or use the search bar to find the what3words widget. Tap to select it, choose from the three different widget sizes, then tap ‘Add Widget’. Tap and hold to drag the widget to any of your phone screens.