How to lock the app?
There are two options to lock TickTick: Passcode and Touch ID.
Option 1: Passcode
Open TickTick on your iOS device and slide the screen to the right.
Tap the gear-shaped icon in the upper-right corner.
Tap "Advanced Settings", then tap "Passcode".
Option 2: Touch ID
After you enable Passcode according to the steps above, you can then enable "Touch ID" in the same page.
Once Touch ID is enabled, the Touch ID sensor will read your fingerprint and unlock TickTick with a touch of your finger.