[Q] topic

Hi guys

Please help me to update my sofware

I got HTC ONE DUAL SIM 802w china unicom
Sofware number-1.0.0.802w
Buil number-1.12.1402.1 CL186762

I bought it in shop and it is still running on Android 4.1.2

I want to update it to latest KitKat 4.4.2.
Please tell me where to start from and is it possible or not???

Many thanks