Can't find an airport?

i've been looking at those travel websites to find CHEAP airfare for 2 adults and 1 ten year old. my problem i don't know where to start. i know what airport i want to end up at (XNA) and i know i wanna be there by 4/19/2008 or even a couple days before. i want one way and i live in estherville iowa. can someone help me find the cheapest route? i don't even know what airport i would start at! never done this before.