so i need this because im driving all the way to s.c and i have an ipod nano and i was wondering how this charger would work

http://www.bestbuy.com/site/olspage.jsp?skuId=8672304&st=ipod+car+chargers&typ e=product&id=1203815033493

like how does the top peice work or do you plug in the cord to that or any ideas?

thanks
=-)