I would like to know this too, it says online its an iPad compatible app but it does not show in the UK app store, however everyone I know with an iPhone has this app?
It's not even available under iPhone apps when searching with my iPad.
The WhatsApp is a cross-platform mobile messaging app for texting on a phone. On their web site - the developers say there is no support for iPad or iPods at this time (read: if it ain't a phone - it ain't working).
You can install WhatsApp on an iPad after you jail break the iPad and install a tweak or two on the iPad that will allow you to download the app. This is not a trivial process and I've read m any posts where jail breakers have issues [also].
Bottom line: WhatsApp is not designed for the iPad and cannot be installed on a stock iPad.
As this issue has been brought up many times here - this particular thread is closed. Thanks for your understanding.