If the seat belt warning key in ignition warning and lights on warning have all been disabled How can you turn them back on?

On the 1987 Honda Accord DX I recently acquired I believe all 3 of those things are controlled by the ICU (Integrated Control Unit), under the dash above the hump. It has one connector plugged into it. Maybe yours has a similar unit that is unplugged.

On my Honda accord there is a seat belt control box that is under then passenger seat. Mine was unplugged and cut all power to seat belt alarms and power seat belts