Overlapping parts - Answer to BlueTaslems Comment - Help?

I know nothing about this subject and solid modeling has nothing to do with it. Go into studio and put 2 parts in. Try and make it so that they are in each other. Well... I can't make them overlap each other and this is the 4th time I've asked this question risking 17 of my reputation. So if you would please answer this question then I would be very happy and this question would not be asked again. I look forward to getting this question banned a 5th time. -_-