Instructions to enable 2FA for Yahoo email are:
• To begin with, you need to log in to Yahoo Mail account and then go to Account Info page.
• Then click Account Security.
• In case it is not enabled, you need to enter the button for turning on Two-Step Verification.
• Just enter the mobile number if there isn’t one linked with account and click Send SMS or Call Me.
• After that you will get a text or call with a code for entering in the verification code field.
• Now, click Verify.
Read More:- http://supportforhelp.bigcartel.com/product/how-to-create-a-new-yahoo-mail-account