Good question. I had to deal with the same question/s with my son at that age as he wanted to play tackle football on a team with some of his kindergarten friends. The basic thing is to keep it simple and basically on two things: blocking and tackling. The other concepts will fall into place as he starts running around and getting more involved, and as he siuts with you and either watches a little football on television or at a live game; preferably older kids maybe 4th or 5th grade so things don't blow by so fast for him.

Blocking and Tackling basixs will help him understand movement and contact and pointing it out and how it is done will give him a better focus on the game than the kid who focuses more on catching the ball, throwing it, and running with it. That stuff will definitely come later.
Peace

I am having the same problem with my son matthew. What do i do if he does not like to do the exercise that the coachs give them to do. As soon as he see that the exercise is over then he wants to get in and play.What do i do.I realy want him to play.

Kids learn by doing and visual actions. Take him out to the yard and physically and visually show some simple plays, what players do on defense and offense, keep it simple, fun and you'll be surprised how fast he catches on. Also like John answer.

u can teach him takes lomg for younger kids but sit down wit him and watch football and as a play is happening on the tv point to the wr or the qb and tell them what they do and he should catch on just keep workin with them

take the hit or give the hit be tough,no crying

you cant... he is 6!

Try watching it on tv with him. point to the guy who plays in a similar position to him, and point out other familiar items. maybe after seeing it all play out, it will get through a bit further with him.