Hello CPmodeler,
You've only given us part of the problem. It would help if you told us whether the chassis/trucks or the body shell gets screwed into those screwholes. An isometric view of the part in your picture + a picture of the other bits which completes the model will help a lot.
In any event, the small green circuit board appears to be a low power simple transistor circuit incapable of delivering power to the motor.... that suggests it is a constant lighting circuit. (This is only a guess). There is also a motor spark generated interferance suppressor in what you show here.
I suspect the brass tabs on the left are contacts which connect to the motor. The two outer tracks of the yellow circuit board appear to connect the wheel pick-ups from the trucks but how that power gets to the motor cannot be established from that single picture.
Post more pictures please of all parts of the loco which have electrical parts attached to them
Errol