Route main mix output to digital input to bounce the mix in protools

I have mix on protools, each track is on digital via FireWire. I want to bounce my mix. I saw on setup (uc control) chael 33/34 is routed to main output. But When I create track with input 33/34 to record main output, there is no signal. I have to route main output to digital output, but I didn't know how. No idea Inside manuals too.

I'm not to be clear ....