Change 2 step verification

Hello,

If you want to sign up for two factor authentication (the newest security method), refer to this support article: Two-factor authentication for Apple ID - Apple Support

If you want to sign up for two-step verification because you can't use two-factor authentication with your account, for example if your device uses iOS 8 or OS X Yosemite or earlier, you can keep your Apple ID secure with two-step verification instead. Read this support article --> Get a verification code and sign in with two-factor authentication - Apple Support

If by "change" you mean wish to disable two-factor authentication, for some background I suggest you read the document: "Two-factor authentication for Apple ID" - Two-factor authentication for Apple ID - Apple Support

Several years ago Apple transitioned to using two-factor authentication for additional account security. Accounts created since that time automatically use two-factor authentication and this cannot be disabled.

Some people have older accounts from before two-factor authentication was mandatory on new accounts. Apple encourages those users to transition to two-factor authentication when signing in on their accounts because without it "your account is less secure and you can't use features that require a higher level of security." Those owners of older accounts who just activated two-factor authentication have two weeks to change their minds and return to older security settings.

If you have an older account, recently activated two factor authentication, and you're within the two week period for turning it off again, you should check for an email from Apple for a way to do this. If you don't see one about this, look in your junk mail folder.