Apple iPad with Retina display

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 lock code, go to 2a.
Turn off lock code, go to 2b.

2a - Turn on lock code

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

2a - Turn on lock code

Press Require Passcode.

2a - Turn on lock code

Press Immediately or the required interval.

2b - Turn off lock code

Press Turn Passcode Off.
Key in the lock code.

Exit

Press the Home key to return to standby mode.