This photo shows the three groups of wires - red, black and white connected together.

There are 3 red wires, all cut to an appropriate length, stripped, twisted together and left like that for now.

Note the red wire from the tender pickup is looped in an S shape. The red wire from the chip is made as long as is possible. That leaves open the opportunity to redo the wiring if something goes wrong later in its life. The ride wire from the loco follows a similar route. The small loop between the loco and tender is checked before cutting to size. Something similar applies to the 3 black wires. There are only 2 white wires - one to the front of the loco and one from the chip.

With the wires like this, the loco can be put onto the track and tested.