The user manuals will help with many of your connectivity and Command Base requirement questions and are available from Lionel:
http://www.lionel.com/products...rmaster-135-6-12867/
Basically, the PowerMaster takes the input voltage of a nominal 18VAC and listens to the CAB-1 remote to vary its output voltage. The PowerMaster in essence works like a single remote control throttle handle.
In general, PowerMasters are not connected to accessories. To add accessory control to your TMCC setup, there are many products out there such as these: