You need to have a Passcode enabled on your smartphone in order to use the TrustVault app.
Step 1: On iPhone X and later, go to Settings > Face ID & Passcode. On earlier iPhone models, go to Touch ID & Passcode. On devices without Touch ID, go to Settings > Passcode.
Step 2: Tap Turn Passcode On.
Step 3: Enter a six-digit passcode. Or tap Passcode Options to switch to a four-digit numeric code, a custom numeric code, or a custom alphanumeric code.
Step 4: Enter your passcode again to confirm it and activate it.