To add a class to your Wish List, simply click the "Save to Wish List" button with the little heart icon next to it. This will automatically add the class to your Wish List and allow you to be automatically notified of when that class has dates added.
To remove a class from your Wish List, click the "Wish List" link in the upper right hand corner of the site (next to the sign in/sign up). From here you can click the "Remove from Wishlist" link beneath the photo of the class you'd like to remove.