You need a big fat cable from the battery negative terminal going to a good sold connection to the frame.
Once that's in, you can connect the harness ground to any spot on the main frame. The tail light gets a ground wire from the harness rather than grounding to the frame because the rear forks aren't really grounded, being mounted on bushings and insulated shocks. The headlight suff is grounded by the green wires in the bucket, again one doesn't want to run electrical power through the steering stem bearings. The front end should also be grounded by a green wire connecting to a terminal on the headlight bucket mounting bolt/nut area.
Different bikes ground the green wire to the frame different places but usually the green wire to the rectifier is one place, the rectifier gets a solid ground to the frame via its mounting bolt.
