Connecting your Facebook account to your Yahoo account allows you to import your Facebook as Yahoo contacts. Connecting also allows you to see Facebook profile pictures in your Yahoo inbox when you receive emails.
From your Yahoo Mail page, click the Gear icon. Choose Settings from the drop-down menu.
In the pop-up, click Accounts. In the Connected Accounts section, click Connect next to Facebook.
In the pop-up, click Okay.
In the Success pop-up window, click OK and then click Save to close the Settings pop-up.
To import your Facebook friends into your Yahoo contacts, click the Contacts tab, denoted by an address book icon, in the Yahoo Mail menu bar. Select Import Contacts.
Click Import next to Facebook.
In the pop-up, click Okay to grant permission to log in with Facebook. Your Facebook friends show in your contacts list after the import is complete.
You can disconnect your Facebook account from your Yahoo account through the Contacts tab or through Settings.
To disconnect through the Contacts tab, click the Contacts tab and then select Disconnect next to Facebook from the Imported section.
To disconnect Facebook through Settings, click the Gear icon and choose Settings from the drop-down menu. Choose Accounts and click Disconnect next to Facebook under Connected Accounts. Click Save to finish.