Go to menu > settings > turn on passcode > enter your new passcode.
You have the option to use 4-digits, 6-digits, or alpha-numeric passcode. Just click on “passcode options” before you enter your new passcode. It’s recommended that you do NOT use a pattern, but a sequence of numbers that you can remember. When you re-enter your app, the numbers on the passcode dialpad is randomized.
If your device supports biometrics (fingerprint or face recognition) your device will ask you for permission to enable these features after you set up your passcode.