.. Creating the battery

We have all of the components, but they need to be combined in a specific order, or you'll just be making a mess.

First, combine the lemon with the copper spoon.
Next, combine that creation with the zinc pyramid.
Finally, combine that monstrosity with the cable.

That's apparently a battery! Return to the train and stick it into the engine-hole on the left.

That's everything - assuming you've authorised the journey and stuck the train key into the control panel on the right.

Talk to Linda and you'll be good to go!