The coomand base with the cab-1 set you bought came as a set? The command base is used for TMCC and Legacy engines that are command equipped.
The powermaster which is black and looks very similar to the base is used for conventional operation of non-command equipped engines. One powermaster per each loop of track and you assign via the cab-1 each loop a TR number 1 through 9 is the limit you get.
Also, you do NOT need a command base to operate the powermaster as the cab-1 has a crystal that talks to the powermaster crystal.
Question is what are you using for a transformer? Reason I ask is stores/ folks who do not know this might give you incorfect information. I heard from folks that bought one of newer ZWs which has the powermaster capability built internally were told that they need to buy powermasters to run non- equipped command engines. Totally wrong.
Let me know what you got there and some here on the forum are very well-knowledged.