How to use atmel studio 7 development watchX?
How to settings external tools when ISP watchX?
Maybe this link helps https://www.asensar.com/guide/arduino_atemlstudio/integrate-avrdude-with-atmel-studio.html
This method I have tried is fail, but using the arduino uno development platform is feasible.
You may need an ISP programmer and watchX Arduino Accessory in-order to reach the ISP pins. Once you flash the watchX with ISP you will lose the Arduino bootloader. Not a big issue, you can re-flash it with an Arduino and Arduino IDE.