Before you remove the magneto. Remove the small distributor cap. Note where the rotor is pointing. When you put the magneto back on the rotor needs to be pointing in the same position as before.
You will have to remove the distributor cap and the coil. The screw is a 6-32 X 3/4 You will also need two nuts and washers. You will have to make a wire. The wire goes from the screw to the screw on the points. On all the type J's I've had a part. The wire runs along the back of the coil and around the right side of the coil and then down to the points.
I use nylon washers for the insulators. You will need an insulator inside the hole as well. I use rubber fuel line for a 2 cycle engines.