Enable security key
Sign in to the Yahoo Account security page.
Next to 2-Step Verification, click Turn on 2SV.
Click Get started.
Select Security key.
Click Set up Key.
Follow the on-screen prompts to finish setting up your Security Key:
If you are using an IDmelon Reader, insert it into the USB port of your device, tap your smartphone to the Reader which starts blinking blue for a few seconds to receive the notification.
If you are using IDmelon Pairing Tool, you will receive the notification on the smartphone which is already paired with your computer.