Before attempting to drain the radiator:
* Consult your owner's manual: This is the best resource for the exact location and instructions for your specific vehicle.
* Let the engine cool completely: Hot coolant can cause serious burns.
* Have a suitable drain pan ready: To catch the coolant.
* Wear appropriate safety gear: Gloves and eye protection are recommended.
If you can't locate it after checking these things, a picture of the bottom of your radiator from the front would be helpful for someone to point it out for you.