Here is how to update WhatsApp on your Nokia S60 device:
Open WhatsApp and go to Options > Settings > Updates.
Click on Check for updates.
Follow the on screen instructions to install the update.
You can also update manually by opening www.whatsapp.com/download/ on your phone's web browser and clicking on Download Now. Note: You do not need to remove or uninstall
WhatsApp in order to update. If you do remove WhatsApp, you may lose
your entire WhatsApp chat history.
Cheers, Source WhatsApp Support Team