To connect your smartwatch to receive WhatsApp notifications, you must first pair it with your smartphone via the Mi Fitness app. Then, in the Mi Fitness app, go to "Device" and enable notifications for WhatsApp. Also make sure to enable notifications for the Mi Fitness app in your phone's settings. This way, WhatsApp messages will come to you as notifications on your smartwatch, but you will not be able to reply directly from your device. For WhatsApp calls, the smartwatch will show the notification and you can reject or mute the call, but you will have to use your phone to answer it.