A quote from their blog site: From Yahoo!'s point of view, any type of signed-in user involving with Yahoo! services is a valued user, whether she validates using a Yahoo!, Facebook, or Google ID.
Yahoo Mail Login with Facebook
Login to Yahoo Mail account on PC/Desktop computer system
First you require a username and password; currently open internet browser from your computer/desktop. After that open web page www.yahoomail.com on it. To initiate their new "one-click" sign-in just click on the "Sign in with: Facebook" icon on the Yahoo! login screen. That's all you need; to get access of your Yahoo mail account.
Login to Yahoo Mail account on Mac computer
If you are an individual of Mac computer then Safari need to be your internet browser. Safari is the best surfing remedy for Mac OS; Safari is quick, faster and easy to use internet browser. You could quickly access your Yahoo Mail account with it. See, the best ways to login with Yahoo mail account on Safari browser. Merely open Safari and type www.yahoomail.com; you will be directed to Yahoo mail sign-in page. To initiate their new "one-click" sign-in merely click on the "Sign in with: Facebook". You are after that fully authorized into Yahoo!
Nonetheless, an advice- you still will not be able to authorize into a mobile or desktop client using Google OpenID.
I hope this article could help you. Thanks ...