Set a lock screen passcode on iOS 6 devices
Use a passcode to protect your iPad, iPhone or iPod Touch
Here's how you can set up a lock screen passcode to protect the information on your iPad, iPod Touch or iPhone in iOS 6.
1. Tap on the Settings icon.
2. Tap on General.
3. Tap on Passcode Lock.
4. Enter your passcode, then confirm it.
For more, see the original article at the link below.
Set a Passcode on Lock Screen | Gotta Be Mobile