Usually if you google it, using the specific model number, you can find a tutorial.
Could you message or post me a pic of your setting page and see if I can figure it out? There has to be a passcodes page because this is where you can have Apple save various passcodes to websites if you want to not have to remember or enter them. They wouldn’t remove that Functionality so it has to be somewhere.They removed the Passwords and Accounts from the setting. Only thing close is Face ID & Passcode; iTunes and App Store and Wallet and Apple Pay. And I'm not going to use Face ID or passcode because I'm only gone from the house 4 hours a week. I even looked at Setting/Mail and still nothing to change the default. I'm very sorry now I got this phone Ugh