1. First of all, you need the bind the watch to the app.
2. Secondly, you should permit all the requests from the app to receive notifications on the watch. Moreover, make sure you have already turned on the apps notification function on your mobile phone, and make sure you have turned on the notification functoin of the apps you would like to receive notification.
3. For receiving notifications on the watch, users have to switch on the function of Preview in the notification settings in their smartphone.