Hi
A warm welcome to this great forum. Here a Märklin digital fan from Paris France

Assumption not enough power: unless the loco is defective the unit you have (MS2 + Trackbox + 36 W PSU) delivers 36 VA enough to power 4 locos running simultaneously

DCC decoder: they are often similar with a factory-set address of 3. The unit can program most of DCC locos

How to program?
- set the loco ALONE on the track
- power on and select a free space on the MS2 (66950)
- select the fonction discover (shift+Loco) scroll down. The MS2 will search for all possible adresses in DCC, MFX, MM2 and report back
- once discovered select modify loco (Shift+ Loco, scroll down & select), select address and key in the new address (either using the side keys or using the rotary knob, validate, finished

Note: depending on the deocer, often, during programming the lights blink to signal the edit mode
Note: if you accidently have more than one loco during the process then you probably changed addresses on all of them. No Problem: simply repeat the process with ONE loco
Cheers
Jean