Preparing a train for any control system is pretty similar ... You need to locate the wires that come up from the wheels and supply power (+/-). You also need to find the 2 wires (+/-) that run to the motor. Then you need to find the wires that run to any lights you would like to control separately. The only gotcha you sometimes have to keep an eye out for is if your motor is grounded directly to the chassis. If it is, you want to eliminate that.
Any bluetooth or other form of board control will generally give you either wires or a place to connect these to.