You need to be logged into your account to be able to change your personal passcode.
To change your personal passcode:
- Navigate to the Account screen by tapping on the tab bar at the bottom of the home screen.
- Tap Personal passcode in the Security section of the Account screen.
- Enter your Current passcode and then create your New passcode.
Note: To check if your passcode has changed, close the app and launch it again. You will be prompted for your passcode and you should be able to get in only with your new one.