If you want to keep your Venmo account safe, you can set a PIN in your account settings as another layer of security. By enabling this feature, the app will ask for that PIN every time the app is opened.
To set your PIN, go to Settings. Under Security you'll see an option to turn on Touch ID & PIN (depending on what you have enabled in your phone settings), then choose your 4-digit PIN. Once you do this, you'll be prompted for your PIN every time you enter the app.
If Touch ID is not an option, please ensure that you have this feature enabled in your general phone settings.
To set your PIN, go to Settings --> Security --> PIN Code & Fingerprint. Once you're there, enable the PIN code and set a PIN of your choosing. If your phone is capable, there will also be an option to use Fingerprint Unlock in Venmo.
Please note that you must have Touch ID or Fingerprint enabled in your general phone settings in order to use those features in Venmo.