setting up an out board controller in Cubase 6

I have a TASCAM US2400 USB controller that I have used for years with Cubase. I have always used the generic “Mackie” controller settings in the device setup menu and it has worked fine. I can’t seem to locate a way to assign all 24 channels of the TASCAM to Cubase 6. I suppose I have missed something in the manual but can’t seem to get it up and running correctly. Any enlightenment from other users would be greatly appreciated!!!