Open the app’s settings
Look for Face ID, Touch ID, Privacy, or Security options
Turn on Face ID if the app supports it
Go to iPhone Settings
Tap Face ID & Passcode
Enter your passcode
Make sure Face ID is set up
Check the app’s permissions in Settings
Open the app again and enable biometric login
If needed, update the app to the latest version
If the app does not support Face ID, use a screen lock or app lock feature instead