The video does explain everything really well.
I did the typical man thing and ignored all instructions. Did the software mod only to find that the program box wouldn't talk to the new software. I hadn't updated the program box!!
Re-did the lot again and hey presto it all looks good.
Watch all the video and even the bit at the very end about resetting the speedo to the transmitter is important. Remember to plug the speedo back into the receiver to do this, I didn't, then wondered why it wasn't working.