So this is what it looks like ingame (Play->Arrow to the right from Ep. 5->Coming Soon Button)
Episode status looks very similar.
So what's the deal? Why can't I access this content yet?
Edit:Alright I got it to work.
Right click on the game in your Steam Library and click 'Properties.' Then go to the 'Local Files' tab. Finally click the 'Verify Game Cache' button and an update should start. Then the DLC should work.