WhatsApp

As fieryjack posted, there is no WhatsApp for the Apple Watch at this time. If it's any consolation, you'll still receive WhatsApp notifications on your watch when, say, a message arrives.

Assuming that you already receive notifications on the iPhone proper, the other thing you need to do is:

1. Open the Watch app on your phone
2. Tap Notifications
3. Scroll down to the MIRROR IPHONE ALERTS FROM section
4. Keep scrolling down until you see WhatsApp
5. Turn the switch on (it should turn green)

There is no whatsapp app on the apple watch, are you talking about "Chatify"?.

Whatsapp is an iphone app.

You have to set them up on the phone.