Plug the correct Wall Wart Power supply into a properly grounded 3 prong outlet. Some outlet strips will cause issues so if you are plugging into a strip and you have signal issues, plug directly into the wall outlet.
Attach the 1 wire from the command base to the common either via the outside rail or the black output lug of the TIU. Depending on the vintage of TIU these 4 outputs maybe tied together or isolated from each other so keep that in mind.
You will not need the orange module for running the Legacy engine with a Cab1.
Depending on how you want to address the locomotive, most people use a 2 number combination of the road number (in your case either 27 or 97), you might want to give the engine a new ID. The default is 1.
To do this locate the PGM/RUN switch. Slide it to PGM, apply track power, push ENG XX (XX being the number you want to give it) and then SET (underneath the cover on the bottom of the CAB1). The whistle should blow. Slide the switch back to RUN. Now address the loco using the number you gave it and move 'em out!