Our SDK/API supports signing in using the popular PlayFab service provided by Microsoft Azure. However, since the PlayFab SDK for Unity can currently only be imported manually via a .unitypackage file, we’ve opted not to include it directly in our SDK as doing so may create dependancy conflicts in your project. Similarly, we haven’t provided any integration code within our SDK. Luckily, the PlayFab SDK is easily integrated into your project. Please see their readme for installation and integration instructions. Once you’ve authenticated your user via PlayFab, you should have received a SessionTicket from the LoginResult object. From here, simply call PlayFabLogin on a SequenceLogin object 
public void OnPlayFabLoginSuccess(LoginResult result) {
    SequenceLogin login = SequenceLogin.GetInstance();
    login.PlayFabLogin(PlayFabSettings.staticSettings.TitleId, result.SessionTicket, email);
}
where email is the email string used to login to PlayFab (or "" if using PlayFab Guest Login).
Don’t forget to subscribe to the SequenceWallet.OnWalletCreated event to receive your newly created wallet!
Don’t forget to configure PlayFab in the Builder!