Firstly, check whether the Touch ID is enabled in the settings of your device.
Now open Outbank and activate the quick login via Touch ID in the login screen:
Tap on Touch ID icon > enter Master Password
Activate Touch ID in the settings of the app:
Menu > Settings > Security > Touch ID > Enter Master Password
IMPORTANT: When you choose to login via Touch ID (after activation), a popup with the following message appears "Outbank is trying to unlock Outbank". Simply unlock Outbank by holding your finger on the scanner. Alternatively you may have to enter your device password, not your Outbank Master Password.