Loading ArduCopter-v2.px4 firmware on Pixhawk

How do you load ArduCopter-v2.px4 file onto Pixhawk .

I found the instructions on how to load firmware but there is so many ways that it totally confuses me.

I have the ArduCopter-v2.px4 file on may Windows7 PC.

This is Firmware 3.3rc5 and this is what I want to install.

Try: http://copter.ardupilot.com/wiki/common-loading-firmware-onto-pixhawk/

Then use the load custom firmware (and point to file on your pc) or turn on beta versions and select from the dropdown box.