To align the three cars of the Harlem train on a single track you will have to use the rotating trading platform and also interact with the cars themselves , pulling them with the help of the cobwebs (press L1 + R1 at the same time and then the Square key repeatedly).
First, then position yourself next to the platform that houses the first wagon. Pull it towards you so that it lines up with the rail. Once done, go in front of the wagon itself (with your back to the tunnel, so to speak), and pull it further along the track, in order to clear the platform.
Now you can think of the next car, which is in the garage on your right. Rotate the platform anti-clockwise again and then tow the second wagon over it, which will then be perpendicular to the first. You have to line it up, then rotate the platform counter-clockwise again.
Once this is done, you will have the last car left: you can see it suspended in the air, hooked to the crane located further back on the track. Climb up there and you will find a gear to interact with. It will be enough to press L1 + R1 to make the wagon go down, but you will also have to block the gear wheel with the cobwebs, pressing R1 repeatedly.
At this point you are almost done! All you have to do is restore the electricity to power all the wagons. Next to the tunnel entrance you will find the generator, which must be reset with an electric fist from Miles: press L1 + Square to restore power to the generator. Finally, use the cobwebs of the wall-climbing friend to connect the generator to the power line, returning power to the subway. If you want more tips on the new Spider-Man game you can take a look at our guide on how to recharge your health or change the time of day.