Insert soft synth in the synth rack as CJ pointed out.
You will need to output your midi track to AD.
I don't think all of AD's outputs are necessary. (They are listed as inputs on the audio tracks)
I use only the mono tracks for the individual pieces and stereo tracks for the room, overheads and FX.
It depends on what your after from there. I don't use AD's effects and just insert the effect I want in the tracks.
If your still having trouble with hearing the drums, make sure the arrows are on in the bottom of the AD UI next to each fader.