Before wiring the loco, we need to reconnect the tender. That means taking off the baseplate again. The loco is in a very precarious position in the photo. Don't follow this example - instead, make absolutely certain that it cannot fall over sideways. If it topple over in this state, the wheels will drop out, and getting the wheels back into position all lined up on their gears, and the valve gear sorted out is not easy. I have some modelling foam sheets, and I often press the upturned chassis into the foam to leave indetations and then cut the foam. That way the top end is buried in foam up to the top of the wheels and it isn't going to fall anywhere.

Note that the baseplate is the wrong way round for the chassis in this photo. The hole at the left end in the photo sits over a stud at the rear onto which the rear bogie pivots. Seprate the two halves of the drawbar by undoing the single screw. You now have two screws for the drawbar. Both are different sizes.