You can choose to enable or disable Touch ID at any time through the 'Profile' menu (the icon in the top right corner on the account list screen) within the app.
You will always have the option of entering your passcode for our app, even if Touch ID is activated.
To use this feature you must have set up Touch ID on your device. For more information on how to set up Touch ID on your iPhone please visit the Apple Support website, https://support.apple.com/en-us/HT5883 (opens in a new window)