Focusrite Octopre

I have been using protools LE 8 for a long time now with my m-audio project mix. It's all been great and I've gotten some pretty cool recordings. In an effort to add a couple more tracks and get some nice sounding pre amps I just bought a focusrite Octopre. I set it up, ran an ADAT cable to the IN on the back of the project mix, and tried it out. Unfortunately it didn't work. I made a new track on protools, picked audio track and when picking an input ADAT was not an option. I am probably doing something really stupid, but never the less, I can't get it to work!!

Any one have any ideas about what I could be doing wrong?

Thanks so much
Harry