Ahhh! I just re-read your question several times and realized something: you're trying to monitor the stereo signal from two other channels. (You say 46/47 in your example, and you could do that, but 47/48 would be more natural.) If that’s what you want to do, here’s how you do it:
You still have to map your stereo output in Logic to any two Firewire channels. Then route those two Firewire channels to the DM channels you want, such as 47/48. Now, you can further process the signal here with EQ, compression, or effects on these channels in any combination you want – this is how I perform some light EQ in my studio to compensate for my Control Room, namely, I boost the top end slightly and all my mixes benefit from that when I’m monitoring them for frequency balance.
So, if you did what I said above in my example and sent the two Firewire channels with your stereo signal from Logic to channels 47/48 in the DM, you now need to send them to a set of physical output jacks that will ultimately connect to your speakers - usually, that's through your DM's Monitor section. Your options here are as mentioned in my previous post: the Stereo Bus, the Aux Sends, or the Busses – these are sources you can select in the monitor section which drives your speakers.
I know one guy (using a different mixer) that doesn't like that mixer's monitor section, so he uses a Presonus Monitor Station I believe. In his case, he sends the stereo signal out a couple of sends to the monitor station and that feeds his speakers. But I think this gives you the idea that you can send any signal or pair of signals (stereo) to almost any output you desire.
As you can see, getting signals around your DAW and the DM is all about mapping. It’s important to first define your source (usually your DAW) and your destination (usually your speakers). Then, you map the path between those two. This path can be simple, short, and direct. Or you can map a longer path to allow you to monitor your mix or even send output to multiple sources, such as through sends for effects, the busses for some parallel processing, the monitor speakers for listening to it all, a recording device (CD, tape, etc.) and one or more cue sends to the talent.
I’m now suspecting that you haven’t “assembled” a complete path to your monitors and that is why you’re not getting any sound. If I’m totally wrong in my conclusion of your problem (wouldn’t be the first time nor the last), please try describing the problem again with as much detail as you can and we’ll try to help.