Two step verification prevents unapproved changes to your Yahoo Small Business account with an extra sheet of security. Users facing issues with How to add a two-step verification code for extra securing in Yahoo? For this you just need to follow simple steps:
Sign in to your Account page
Under Account Security, click Turn on two-step verification using the above phone number. Link.
Confirm your phone number then click the Continue button.
Enter the verification code we've sent via text and click Verify.
I hope it will help you to enable two-step verification in Yahoo, if not then you can always call our Customer Support Number +1(909)-242-8633 available 24/7.