In order to teach the very basics, such as pieces movement, you can play simplified chess variants, such as only pawns, knights game, etc.
After the very basics, one approach is to play easy endgames: that should help to make it clear from the outset that chess is not about moving your pieces around, but to try to checkmate the opponent. About checkmate, though, you might as well skip it for now and let the games end by the capture of the king as a further simplification.
The next step is probably to make her notice there are less and more powerful pieces. Or you could be to try to get them to realize there are some very bad and some very good openings, or just do some free play, giving tips here and there. The best approach will strongly depend on the individual child. There's some more specific advice in this forum thread and in this answer. BTW, at Chess SE you can probably find chess instructors who'll be able to give qualified advice.
When the kid becomes interested enough, taking part in a chess club, association or similar would be of great help.
Lastly, if you'd like this kind of tool, this site looks promising and I've seen it recommended.