I accidently put antifreeze in my 2001 cadillac sts northstar engine. I did NOT start the car yet but I want to know the best way get it out and will it ruin my engine. Car has been sitting for about a month and had very little engine oil in the car to begin with. Less than a 12oz drinking cup was put in.
You didn't specify where you put the antifreeze, but I assume it is mixed with the oil now. As Paulster2 said, replace the oil now (or later, but not later than starting the car)! Don't start the car before replacing the oil, if there is any significant amounts of antifreeze in the oil!
Lots of people drive with small amounts of antifreeze in the oil due to a damaged head gasket. After the head gasket is replaced (along with an oil change), the engine won't die an early death. However, I believe you have more antifreeze in your oil than what those head gasket problem cars have, so as a precaution, I wouldn't start the car before an oil change.
Antifreeze is compatible with all metals used in engines. It has to be. So, the only way it could have harmed your engine is the reduced lubrication effectiveness of the motor oil. So, it won't dissolve your precious components in the engine. Because you haven't started the car yet, the damage due to poor lubrication has not yet happened.
By the way, you said there was "very little" oil. This seems suspicious. Typically on an engine with 4L oil capacity, the minimum line is 3L, which I wouldn't consider "very little" as it's 75% of the capacity. How much is "very little"? Was the oil amount below the minimum line? If it was below the minimum line, you may have already damaged your engine by running it with too little oil.