Kari is right in that there are no desktop versions of Whatsapp, the only official builds available are for Android, iOS and Windows Phone, all phone-oriented, and the only way officially supported.
There are at least two ways you might try to make it run on a desktop PC. See this link:
How to install whatsapp on PC Laptop & Desktop (MAC & Window) Complete Steps A 2 Z - YouTube
Here, an emulator is used on Windows to emulate the Android OS, supposedly Whatsapp runs well on there. I've never experimented anything like that, but it might work. The comments on the video don't look that promising, but it's at least something to try if you REALLY want.
Another option, possibly even more complicated, is to install Android itself in the computer alongside Windows or (preferably) as a VM under Windows. There is a native x86 port of Android intended to be run on PCs available here:
Android-x86 - Porting Android to x86
It might be able to run Whatsapp (I have serious doubts, but may be worth a try). In any case, it's not an easy process, and again, the only supported way is to use a phone, unfortunately.
