Youtube, just like everything else. But, this is probably a works-on-my-machine because Youtube isn't the obvious answer for you and even if it were, it's not

Youtube, just like everything else. But, this is probably a works-on-my-machine because Youtube isn't the obvious answer for you and even if it were, it's not the obvious learning method for your wife. ...and because I pay for Youtube Premium so it's more of minimal marginal cost than free. Anyway, my free advice is pay a local musician for banjo lessons. Good luck.