WhatsApp is a great way for sharing content on a more individual way to your friends and acquaintances. However, its experience is limited to mobile devices and thus only available on GetSocial's Mobile Share Bar.
Providing a WhatsApp share button to desktop visitors would be faulty as they won't be able to share through those channels without a mobile device.
This also applies to SMS, Telegram, Viber, Line, and kik as well. If you're looking for Instagram or Snapchat, check the Follow Bars and the Mobile Follow Bar, respectively.
To make WhatsApp available as a share button, just go to Mobile Share Bar and add it to your share bar: