Laravel 5.5 add pin password to built in authentication

I'm writing my very first application with Laravel and are days I'm trying to figure out how I can add a second field for authentication. Let me explain better, I would like that during registration, the user must choose a pin password (5 numeric digits) in addition to the user and password and that during the authentication phase is requested together with the password before authenticating the user. How can I do that ?

Thanks for your help

via Chebli Mohamed