Once installed, you do not need to run this application, it will always be active. This download is sizable, but will update your L4D2 installation to allow running ANY map, including custom maps made for the original Left 4 Dead. Look for the entry labeled Left 4 Dead 2 - Add-on Support click and install it. Just go into steam and open up the Tools tab. PLAYERS: If you are not looking to design but play custom campaigns all you need to do is install the add-on support package. We are releasing the Left 4 Dead 2 Authoring Tools and Left 4 Dead 2 Add-on Support today.
