How do I add the TruTeq SmarToo on the system?

First you add the way it communicates.
This can basically be the SmarTee, or a Generic APN modem, or a Generic Active GPRS modem, or even a Passive or Active Etherpad.
Then after you've got the comms device, you add the RTU device on top of that.
So, although it is 1 device, it is 2 entities on PNPSCADA.

The 'etherpad' options are there for cases where we communicate with the SmarToo through the RS232 port that is conencted to an Etherpad.
Then we do AT commands on the modem, and don't use the cell phone engine at all.
Therefore, you certainly won't be able to multi-drop SmarToos on etherpads!