Ionic 5: How to Secure Mobile Apps with Fingerprint AIO

I'm using a fingerprint AIO to secure my mobile app, but I'm a little confused as to what to do here. As far as I know, this library only exposes 2 functions isAvailable()and show(). So I try it in my project:

  import { FingerprintAIO, FingerprintOptions } from '@ionic-native/fingerprint-aio/ngx';

  initFingerprint() {
    const opt: FingerprintOptions = {
      title: 'Fingerprint - FaceID authentication',
      subtitle: "It's quick and easy",
      description: '',
      fallbackButtonTitle: 'Use Pin',
      cancelButtonTitle: 'Cancel',
      disableBackup: false
    }
    this.faio.show(opt)
      .then((result) => {
        console.log(result)
        // What should I do here ???
      })
      .catch((error) => {
        console.log(error);
      })
  }

The above function works fine, but in the then()callback how can I do it ? How can I tell my server that this user has successfully authenticated with their finger (or face)?

My assumption is that I need to encrypt their username and password in a text file and then decrypt it after they successfully authenticate and send that information to my server. But that seems like a lot to do.

P/s: here is the library : https://github.com/NiklasMerz/cordova-plugin-fingerprint-aio