1. Click "Settings" on the device's home screen, and tap "General."

2. Tap "Passcode Lock" and tap the "Simple Passcode" to activate or deactivate the simple passcode feature. When activated, the simple passcode consists of only four numbers whereas the alternative is a combination of numbers and letters.

3. Touch the "Turn PassCode On" tab, and create a passcode for the phone.

4. Touch "Require Passcode" and tap "Immediately" to always require a password when accessing the phone.

5. Return to the previous menu and tap the "Erase Data" tab to erase your iPhone's information if the phone's passcode is entered incorrectly 10 times.