Nokia Lumia 820 - Where can I find information about WhatsApp, Skype, Angry Birds, Twitter, NimBuzz, Viber, Fring, or some other non-Nokia application (3rd party application)?
For information and support, check the vendor’s website.
If you have a Nokia Lumia phone, check the Microsoft Store for download. If you have some other Nokia phone, check the Nokia Store. Easiest way to download the application is to use Store app (or Marketplace) on your Nokia phone.