It screws out.
Look at the bottom or rear of radiator
Standing in the front of the truck, It will be on the inside of the bottom right corner of the radiator.
It will be on the inside right bottom side of radiator. HARD TO SEE.
Should be a plug at the bottom or rear of radiator or remove the lower hose
first thing you need to remove the plastic cover from under the truck. there is a screw right under the radiator you might need to fell of it.
(2003 Frontier) From beneath the truck, pull back the leading edge of the rubber splash guard that is below the radiator (it is held in with push pins and 1 Phillips screw). Once this is pulled back you can see the bottom of the radiator. In the center there is a plastic plug with a Phillips head. This is the drain plug. Unscrew it with a screwdriver and the radiator will start to drain.
At the bottom of the radiator, you can see it from under the truck.
bottom driver side of radiator
Bottom of radiator, or possible on the lower hose connection.
For non fuel injected models, on the side of the carburetor there is an idle screw. Turning the screw slightly will raise the idle on your Chevy truck.
It may be inside your radiator itself.
get under the truck and look up. should be accesable from there.