FirebaseUI/Auth with Email-Password

I'm hoping to use FirebaseUI/Auth with Facebook, Google, and email/password authentication options.

On this page, it shows how to add Google and Facebook providers:

FIRGoogleAuthUI *googleAuthUI =
[[FIRGoogleAuthUI alloc] initWithClientID:kGoogleClientID];
FIRFacebookAuthUI *facebookAuthUI =
[[FIRFacebookAuthUI alloc] initWithAppID:kFacebookAppID];
authUI.providers = @[ googleAuthUI, facebookAuthUI];

How would I add email-password to the auth providers option and have it appear on authViewController?