To reset the code for your First Alert 4005DFB Anti-Theft Safe, here's what you need to do: Open the safe using the current code or the emergency key. Inside, locate the small reset button (usually on the inside of the door). Press the reset button, and you'll see a light come on. Enter your new code (3-8 digits). Press the “#” button to confirm your new code. Close the safe and test the new code to make sure it works.