assuming that you have a working ADB, enabled in the setting mode(developer mode) on the Smartwatch, you check if the device is accesibile:
C:\>adb devices
List of devices attached
* daemon not running. starting it now on port 5037 *
* daemon started successfully *
QEV6N97543000021 device
If you wanna uninstall a older version for not working because of waning that the version is too old
#Uninstall Whatsapp
C:\>adb uninstall com.whatsapp
Success
#for install a new version
C:\>cd C:\Downloads
C:\Downloads>adb install WhatsApp_Messenger_v2.19.274.apk
2872 KB/s (26060210 bytes in 8.860s)
Success
So please check on Smartwatch whatsapp, you may need a font resize app like BigFont in order to see all the message from whatsapp.