How to introduce atheism to children?

I did not introduce atheism to my children just as I did not introduce theism to my children.  As far as I know, all of my children are atheist.  We've never discussed the issue. I did not go to church by the time I had children, none were baptized as helpless infants, I never sat any of them down and said, "Now I don't care what you believe, but...."  Religion simply did not enter the parent child relationship, I guess. When the kids were a bit older- say10 or 11 or so- and friends would want to drag them off to Sunday School I always said, "Okay" and away they'd go, once, maybe twice.  Never for long, never as a habit.  I think they realized that the fun they thought their friends were having at this sort of gathering came at a price, and the price was your willingness to abandon your self to yet another flavor of authority.  My kids weren't generally happy with authority for authority's sake. When my eldest was a teen, he invited Mormons on their mission in- by appointment- because he wanted to know what it was all about.  I was polite, we all sat around the table and talked for awhile.  After about 20 minutes, Son #1 lost interest, but I gave him a mother's gimlet eye:  "You started this, these are your guests.  You have to get rid of them" and then inadvertently gave him the tools to do so when I thoughtlessly blurted out, "You went to college and you believe this?!?" to some point of doctrine or other-  I think it was lost tribes coming to South America in underwater boats or something.  It was all still polite, but they didn't come back. I think, if you witness a religious authority provoking hate speech based upon religion, or doing anything, really, outside the bounds of their own church/group, you have the right and authority to counter such with reasonable discourse, if you please.  But I also think religion has a place for many, many human beings; that religion is a comfort many humans need and have no other way to fulfill-  I think that might be part of being human, this inability to accept the void of unanswered metaphysical questions, and so I do not advocate for an end to religions or churches or faiths.  Teach your children what you will;  hopefully, you will teach them how to think, they will think for themselves, and religious bigotry will end.

I'm a teenager aged 16. My parents never forced our religion (Hinduism) upon me, although I did participate in rituals/festivals as a child. I was brought up in an environment which favoured rational thought to religious superstition or belief. As I entered my teen years, I was exposed to the world of science and its rational approach in ascribing and relating cause and effect. Because my mind hadn't been "brainwashed" by the imposition of religious teachings ALONE, I could absorb what both the theist and atheist sides had to say, and preferred atheism. Now I consider myself to be Irreligious. Bottomline, I as a parent won't fill my child's with either theistic teachings or atheistic ones. I'll simply expose him/her to both, unintentionally, as he/she grows, and then let them decide what they want to believe in. "Introducing Atheism" is not required at all.

Educate them .! will do the trick.!!

There's a fantastic BBC show about religion. It is called Around The World in 80 Faiths. Peter Jones travels the world and investigates some of the surprising ways the people worship and believe.  But in my view, there is no way to watch this show without concluding that what we are seeing is an attempt to meet a common human need, rather than some common supernatural cause for all this activity. If you accept there is no common supernatural cause - and that religion is merely a set of cultural phenomenona - then that is pretty much what atheism is.

Children may be naturally atheistic until their minds are filled with fantasies about supernatural deities along with threats of "damnation,hell, heaven," etc. The Priest-craft and dictators like Hitler have always indoctrinated children because they realize that young, impressionable minds are easy to control. Look at all the young "suicide bombers," martyrs, etc. This is the indoctrination of young minds for nefarious purposes! One way to counter these mind-control operations is to be very careful concerning where you send your children to school and know what they are being taught and by whom. Otherwise indoctrination is inevitable to some degree.

You shouldn't.  You should not "introduce religion" to young children, at all.  They are too impressionable.  These should wait until the child is truly capable of individual analytic thinking, then they should receive the information without bias and be left to make their own choice.