http://www.iykpqm7jiradoeezzkhj7c4b33g4hbgfwelht2evxxeicbpjy44c7ead.onion/deeplinks/2017/09/guide-common-types-two-factor-authentication-web
Luckily, it's becoming much more common across the web. With often just a few clicks in a given account's settings, 2FA adds an extra layer of security to your online accounts on top of your password.