I don't think you can. I've dragged a few of my most used apps onto the dock and turned the recently used apps thing back on again. It can make your dock ridiculously small though. I was initially confused by the fact that the dock is different from the Mac OS version, in that it doesn't just contain a shortcut but the app itself. I managed to delete an app by removing it from the dock!! I'm sure we'll get used to it in time.