Having your Mobile device secured should be a priority for all iPhone users in the event of a lost or misplaced device. Any device iPhone 5s or newer will also allow for a finger print to be used to unlock the phone.
Set your passcode
1. Go to Settings > Touch ID & Passcode. For devices without Touch ID, go to Settings > Passcode:
2. Tap Turn Passcode On.
3. Enter a six-digit passcode. Or tap Passcode Options to switch to a four-digit numeric code, a custom numeric code, or a custom alphanumeric code.
4. Enter your passcode again to confirm it and activate it.