Thousands of WordPress websites are using the bbPress 2.0 plugin to seamlessly include forums. When you first install the plugin it usually fits in fairly naturally with your existing WordPress theme and most people don’t even need to create an entirely new bbPress theme.
That’s where the bbPress Custom CSS File plugin can be handy. It causes bbPress to use a bbpress.css file that you add to your theme directory, instead of the one included in the bbPress core. This lets you keep all of your stylesheets in the same place for easy access. Download bbPress Custom CSS File from the WordPress plugin repository for a more convenient way to theme your forums.