Your question is a little vague. Why can't you connect? It because you have an issue setting up the software, or because the drum kit and the software are in different locations?
I don't know anything much about either the DM Lite or the DT-1 software.
But I do know this. The DM Lite has midi out of a USB port. So step 1 is to connect the DM Lite to the PC via USB.
Next make sure the PC can see DM Lite as a midi device. Google how to do this.
Once you are sure the PC can see the DM Lite, run the DT-1 software and setup it's midi. I have no idea how to do that but it will be there somewhere. RTM!!