Follow the mentioned steps :
Step1: Before beginning let me tell you that you must have to have yahoo account then only you can do this, thus if you donít have any first make it from HERE.
Step2: To chat with your Facebook friends you will first have to link your Yahoo and Facebook accounts. You can do that from within Messenger by completing the "Link to Facebook" flow. This flow can be initiated from two places. If you have created a new ID so whenever you login for the first time youíll get the screen as mentioned in the figure below:
Click the Link to Facebook banner within the main window.
Step3: if you already have an account so you can do the same thing by opening Messenger > Preferences > Connected Networks tab and then click the Add Facebook button. Refer the below Image:
And then select another option mentioned in the figure below :
Step4- Once you have linked your Yahoo and Facebook accounts you will be able use the following procedure to sign in to, or out of, Facebook Chat:
- Click the Messenger menu, or right-click the Facebook Friends contact group.
- Select Sign in to Facebook Chat or Sign out of Facebook Chat
When you are signed in to Facebook chat, just double click a Facebook friend's name to start a conversation .