Extending CWebUser

Pardon my stupidity but I’m unable to overwrite this class to place some more things in login/logout actions. I created a new class WB_CWebUser which extends CWebUser and what to do with it now? Currently I use Yii::app()->user->login but how do I instruct Yii::app()->user to use my new class?

Found it, it should be added in the config file. You can delete this thread, sorry.