how do I put freon into my ac compressor?

Look under the hood for the larger of two fittings on the a/c tubing. They should have caps screwed on, the high pressure side with a red cap, the low pressure side with a blue cap. Buy a recharge can with a gauge and tubing fitted, at Advance Auto, Auto Zone, O'Reilly's, etc. Remove the blue cap, connect the refrigerant (Freon) can, and start the engine with the a/c on. A pretty simple procedure, but follow the instructions with the recharge kit.