question

I would start with these two tutorials, which walk through all the aspects of logging in, linking, and unlinking accounts:

https://api.playfab.com/docs/tutorials/landing-players/best-login

https://api.playfab.com/docs/tutorials/landing-players/account-linking

But we also have tutorials on getting started with Facebook, Google, Kongregate, Steam, Twitch, and Windows in our tutorials page, here:

https://api.playfab.com/docs/tutorials#landing-players

If there's something specific you're looking for which isn't covered there, could you please post it to the Feature Requests forum, so that others can vote on it (which allows us to track on how much of our community needs it)?