Those are drop-in decoders, it means you don't need to solder, just fit them in the right position and in the right place.
To install the motor decoder, slide the undercarriage plastic piece in the direction that points the arrow and remove one of the bogies. Bogies are clipped, so you only need to turn it and pull gently. Insert the decoder with the side having the short contact pads facing to you.
For the cab/end car, just open the hatch and remove the plastic piece. Decoder is inserted with the face having four contact pads towards you. But take a look to the photo, there are two tiny contact pads at the narrow ends that will help you orient the decoder. The one in the cab car is inserted in the opposite direction that the one in the tail car. If you don't do it in this way, the same lights will be illuminated (both red or both white). To fit the decoder, press it against the carriage and with the help of a tiny screw driver push it to the front of the car.
And that's all, pretty easy!!!! Enjoy it running!!!