1. Change on the Watch 3 Pro:
Press and hold anywhere on the home screen for 3 sec. This will open the watch face change selection interface. Swipe left or right and tap the desired watch face to select it.
2. Change in the Nothing X app:
(1) In the Dial gallery, tap on a watch face to view its details. Tap Change Watch Face to change the watch face on your Watch 3 Pro.
(2) In the Dial gallery, tap on a watch face to view its details. Tap Download to download the watch face to your watch. Once the watch face is downloaded, it will be displayed on your Watch 3 Pro.