Pro tools LE plus Eleven Rack. Audio Interface required?

[needled39]

I own a Mac book pro, and I recently purchased an Eleven Rack unit. I installed Pro Tools LE on my Mac Book, and when I open it up everything is working great but I am getting no audio on my actual track.
The Eleven Rack window opens up no problem in Pro Tools, I've edited my sounds and all that stuff without any issues. But when I create a track, I get nothing.
The input was set to guitar originally (which I think would be the right input) but I tried both Eleven Rack L and R inputs just to check and those gave me nothing as well. I know you need an audio interface if you are running M-powered pro tools, but I thought the whole point of the Eleven Rack was that with LE you could just plug it in and go.
Am I doing something wrong here or do I need to get an audio interface?

(I am entirely new to Pro Tools so it could be a very simple step I've over looked)

Any help would be appreciate, thanks