This quote can be found on Act III, after the "big reveal". The reveal refers not only to the truth that Torvald discovered about Nora's dealings with Krogstad but, most important still, the reveal that Nora discovered about Torvald: That he cared nothing for Nora's sense of sacrifice, for the risks she too on his behalf, for the anxiety that she experienced trying to get both her father and Torvald to come back from illness, and for the role that she played, for once, as an initiator rather than a puppet of her husband's ideals.
After Torvald discovers what Nora did, he outdid himself in calling out just about every insulting comment about her behavior, ommitting completely any praise for all the risks that she took for him. He called her a bad mother, a bad person, and an ignorant, thoughtless woman in not so many words.
As she is listening to this, Nora is slowly coming out of her bud and began to see Torvald's real self. And her own. She could not believe her eyes when she heard all that from her husband. She realized that, if she were to be a bad wife, Torvald has been equally a bad husband. Yes, he is a provider, but he does nothing to go beyond his role as a provider to try and understand her.
However, there is a twist to this as well: Torvald had the nerve to tell Nora not to leave him on the grounds that, from that moment on (as he says in his own words) "play-time shall be over, and lesson-time shall begin".
In other words, he gives himself the entire power to rule over Nora past, present, and future.
All this being said, Nora replies the quote which we are analyzing:
Alas, Torvald, you are not the man to educate me on how to be a proper wife for you.
Therefore, Nora basically said "this charade is over. You are less than an ideal husband, and I have been foolishly following you for the sake of social expectations". And, to much of Torvald's shock, she actually took off and left. Which has been a much argued ending to a play written during a time where women were shun from society if they dared leave their husbands or children, much less if it was for the so-called "weak" excuse of trying to find themselves.