The turn signal flasher is under the instrument panel to the left of the steering column brace. On the Bonneville, it may be on the left side on the shroud. The hazard flasher is under the instrument panel to the right of the steering column.
The turn signal flasher is installed in a clamp attached to the base of the steering column support inside the car. In all cases, replacement is made by unplugging the old unit and plugging in a new one.