You must have access to metal of the target conductor (remove all rust, paint, coatings, etc.).  Connect the red terminal or clip to the target, and the black to the ground placed 90° and as far away as possible from the conductor and away from any known adjacent conductors.  If using a Model 100 or 500 High-frequency transmitter place it 90° to the run of the target line as well (this helps prevent bleed-over onto lines running parallel to the target).