How do I tap his wires

First, you'll need your wire testing kit.  Take it out of your inventory.

Look at the diagram on the box.  It will say where to put each wire.

Each color matches one of your wires.

Look at the gauges on the phone box.

Notice how they move into a red zone every once in a while?

Well, never do anything when the gauges are red!

Now look at your wire tester.

If it flashes red, remove the clip that you just put on.

Just don't take long enough for the rats to get you.

The red clip goes on the red wire, and the blue on the black.