Gaston, welcome! Do you have two M84? The MS2 uses a round multi pin cable and connector to a track box. The box has female pin jacks for two MS-2's. The transformer, or wallwart is a 120 volt or 240 volt ac to 36 watts dc voltage at 18 volts.
The MS2 recognized MFX devices and Locomotives automatically, or Marklin Motorola format or other brand DCC ones by manually entering them. M-83 and M-84 decoders are MFX. K-83 or 84 accessory decoders were 16 volt ac devices. So, you would isolate them from a C tracks with the red pointy plastic push in isolators between tracks. Two at each end as explained in the manuals. You then wire another 16 volt output transformer to the isolated track block or blocks, using the accessory terminals on that transformer, which can also be used for lighting. Remember to keep the B and O terminals wired to all tracks the same to prevent short circuits.
I hope I helped you.