"If you’ve upgraded to Yahoo! Messenger 10 or got a new webcam recently, chances are you’ll want to try out the high-quality voice and video call features.Continue reading : Setting up voice and video in Yahoo! Messenger 10
As a first step, we recommend that you complete the “Voice and Video Setup” steps to ensure that your microphone, speakers/headphones, and webcam are working properly.
To get started, click on the Messenger menu and select “Preferences”. When the Preferences window opens, click “Video & Voice” on the left hand menu. This will bring up your options on the right hand side:"
Posted by Sarah Bacon @ Yahoo! Messenger Blog