How do I reconnect the heater or heater core to my Honda 1989 CRX? It was unplugged by a mechanic years ago.?

Years ago I was experiencing some leakage on the front passenger side floor (where the passenger's feet would be) in my Honda 1989 CRX. After taking it to a few mechanics this leak proved to be more of a conundrum than anticipated. One of the mechanics decided to disconnect the heating system to see if that was causing the leak issue. After a while the leak was still there but since we were experiencing warm weather and I didn't have to drive the car on a regular basis I never went back to get the heating system reconnected. Now I have to drive my CRX on the daily and am freezing at most times in the vehicle. I've checked for any leakage in the car (passenger side floor) and haven't seen excess moisture even after all this rain we've had. If someone could give me some pointers on how to reconnect the heater, and any ideas as to what might have caused the leakage it would be very much appreciated. Thank you!!!!