Setting a home page to Yahoo! depends on the browser that the user is running. Typically, changing the home page of a browser is accomplished by going to the "tools" or "options" section of a browser's taskbar or toolbar.
To set Yahoo! as the home page in Internet Explorer, go to Tools, followed by Internet Options. Then enter Yahoo! under the Home Page option. In Google Chrome, set Yahoo! by clicking on the icon that looks like a wrench. Next, find the home page setting under Options, then Basics. For Mozilla Firefox, set the home page by navigating to Tools, then Options, located in the Firefox toolbar.