The barrel you use to start the car with the key, is probably not even plugged in. you just need to remove it, then you need to take the immo ring off this and put to one side.
Then you need to get the other barrel thats hidden, unplug the immo ring and remove the lot out the car.. Take the immo ring off this barrel and place on the other barrel you took out first which you used to start the car.
Put the barrel you have just put the immo ring on back into the car where it should go and plug the immo ring in.
The key I presume looks like this, with the immo transponder attached

Remove the transponder from this key and place into your normal key that starts the car, if there is already one there remove it and place to one side for safe keeping..
You should be all good now.