http://gopro.com/support/wifi-bacpac...emote-support/
The process depends on if you have hero or hero 2. The best bet is to watch the videos on the gopro site, as the process is fairly long, but they detail it well.
I did follow the process, but after reading some of the user
forums one possible issue was I used a PC with USB3 ports and that has been reported as a possible cause of the problem. I will use an old laptop with USB2 ports when I get the replacement.
It's shame that they had some bugs with the wifi backpac out of the box as it has lead to some people having issues trying to flash the firmware.