Apple iPhone 5c

Find "Passcode Lock"

Press Settings.

Find "Passcode Lock"

Press General.

Find "Passcode Lock"

Press Passcode Lock.

Select option

Select one of the following options:
Turn on use of phone lock code, go to 2a.
Turn off use of phone lock code, go to 2b.

2a - Turn on use of phone lock code

Press Turn Passcode On.
Key in a phone lock code of your own choice.
Key in the same phone lock code again.

2a - Turn on use of phone lock code

Press Require Passcode.

2a - Turn on use of phone lock code

Press Immediately or the required period.

2a - Turn on use of phone lock code

Press Back to go back to the settings.

2b - Turn off use of phone lock code

Press Turn Passcode Off.
Key in your phone lock code.

Return to the home screen

Press the Home key to return to the home screen.