Programe the auto lock feature at MPH?

I have an E90 and I just bought my wife an E83 (2008 3.0). One feature that I know is turned off from the dealer, but can be turned on is the auto locking feature when you hit a certain MPH. I have no idea how to do this. I have tried to pick it up along this forum, and I see others give coding, but how do you enter those codes?

I would appreciate the help, as i would feel better if the doors were locking while she drove around, especially with the kiddies in the back seats.

Thanks,
Doug