First off it's not my plug-in, it is Alan's I just helped beta test it. (Alan also did the device manager, and is working on a new CADDX plug-in)
Second you have to make the PC connector/connection yourself. There is a pdf posted in the HS forum with the wiring diagram. It is a rather easy connection to make as there are only 4 wires for the communicating part of the tstat. And to add the second, third... you just connect the 4 tstat wires to the together (parallel)