Where do you add freon on a 2000 Buick regal?

You don't add Freon (refrigerant) yourself to a 2000 Buick Regal (or any car for that matter) unless you're a trained and certified technician with the proper equipment. Improper handling of refrigerant can be dangerous, and doing it wrong can damage your car's air conditioning system.

To recharge the AC system, you should take your Buick Regal to a qualified mechanic or an automotive air conditioning specialist. They have the necessary tools, including gauges to measure pressure and prevent overfilling, and they'll also be able to identify the cause of the leak if there is one. Simply adding refrigerant without addressing a leak is a waste of money and won't fix the problem.

There's no single "add Freon" port; the location of the low-pressure service port (where refrigerant is added) varies slightly depending on the specific model and year. Trying to find it yourself without the proper knowledge could lead to damage or injury.