You can share watch faces from your Apple Watch with your friends. You can also send watch face extensions from other developers. It's very simple.
On Apple Watch, show the watch face you want to share:
1. Touch and hold the display, then tap the share button;
2. Tap the name of the watch face, then tap “Don’t include” for any complications that you don’t want to share.
3. Tap a recipient, or tap Messages or Mail;
If you tap Messages or Mail, add a contact, subject (Mail), and message;
4. Tap Send.