To replace the Pitman arm, remove the nut holding it in place, pull the arm from the shaft, and then disconnect the Pitman arm from the centerlink. Once the old Pitman arm is out, put the new Pitman arm into place.
To start the process of removing the Pitman arm, jack up the car on the left side, and then remove the wheel. Find and remove the nut that holds the Pitman arm in place on the steering box. This is a large nut that is difficult to remove in some cases. When the nut is off, take the Pitman arm puller and remove the arm from the steering shaft. This releases the shaft, but the arm stays in place due to the centerlink.
After the shaft is loose, remove the nut and cotter pin that hold the Pitman arm and centerlink together. Take a puller, and separate the two by pulling down the centerlink and slipping the Pitman arm out. If the Pitman arm does not come out easily, try removing the two bolts that hold the idler arm down, and then pull the Pitman out.
When the Pitman arm is completely removed, place some antisieze grease around the steering box, especially around the bolt with the taper. Prepare and cut the cotter pin to match the old one, wipe away any dirt and grease, and then repack the area around the steering shaft with grease before placing the new Pitman arm in place.