When you download the app, you have the ability to set a PIN. If you would like to enable/disable your PIN, go to ‘Settings’ in the Whisper app and select the PIN option under "Privacy".
Here you will be prompted to enter your personal PIN number twice to complete the process. If you already have a PIN, it will require that you enter your pin to disable the PIN.
Forgot your PIN and need to reset it? No problem!
Please be sure that you have posted multiple whispers before attempting to reset your PIN. Next, select "Settings" on the bottom left to reset your PIN. Once in Settings, select "Forgot PIN". To make sure that you are the owner of the account, you will have to choose a Whisper post you previously created from a list of Whispers. Once you identify the post, you'll be prompted to set your new PIN.
Click here for more information on creating a Whisper.