abt application

The WhatApp developers have not released an App compatible with iPad - the App being currently limited to iPhone.

Whilst the App is not available for iPad - you should be able to access the service using a web browser:

https://web.whatsapp.com/

you can't use the official WhatsApp from facebook they only make that compatible with iphones

there are third-party apps in app store you can use but as far as I know, they are pretty much just an encapsulation of their webapp