Perhaps I misunderstand your question but if you want to set a dcc address for the Smail my understanding is it is programmed in a similar way to a light-It decoder.
There is a program button on the SMAIl. Press it and on my Powercab there is an Accy button. Just after the program button is pressed you would have 1 minute to press accy, and a number that you want to set as a dcc address.

Here are he instructions from their web site.

THE SMAILTM COMES ALREADY SET UP WITH THE MOST POPULAR CV SETTINGS FOR NORMAL USE. THE SMAILTM CANNOT BE PROGRAMMED ON YOUR PROGRAMMING TRACK. IT IS ALWAYS PROGRAMMED WHILE CONNECTED TO THE MAINLINE DCC TRACK POWER.

Procedure for programming Accessory CVs with an NCE or other system providing Accessory OPs Mode Programming:

1) Press the [PROG/ESC] button on your cab.

2) Press [7] to go to the Program Accessories menu.

3) Press [ENTER] to access the menu.

4) Follow the menus to program the desired CVs.

Procedure for programming accessory CVs with a Digitrax, Lenz, MRC or other system that DOES NOT support Accessory OPs Mode Programming:

1) Press the programming button on the SMAILTM to enter programming mode.

2) Use your DCC system to use locomotive OPs mode programming to the desired CV.

3) The SMAIL will accept locomotive OPs programming commands at any locomotive address while the LED is flashing.

4) The LED will stop flashing after 60 seconds or when an OPs CV programming command is received.

5) Repeat the process for each CV you wish to program.

THE SMAILTM WILL ACKNOWLEDGE THE PROGRAMMING OF EACH CV BY ???EXERCISING??? THE SWITCH MACHINE (MOVING IT FROM ITS CURRENT

POSITION TO APPROXIMATELY THE HALF WAY POINT THEN RETURNING TO THE ORIGINAL POSITION) AND LIGHTING THE LED. ONE EXCEPTION IS THE PROGRAMMING OF CV556 WHICH WILL ONLY BRIEFLY FLASH THE LED.