If you need a tutorial for something that’s supposed to be as simple and transparent as a website authentication, your standard has already failed the usability test.
From a user's perspective, if the implementation sucks, the standard sucks.
since the person I responded to couldn't find it, I linked tutorials. it amounts to opening the Settings app, going to "General" and then "AutoFill & Passwords", so it's also not terribly difficult to find compared to other iOS settings.
you could've at least tried to understand what's being talked about before blindly complaining.