So there you have it. If you walk into any participating comic book store—obviously you are not getting this in the supermarket—you will get a free comic book. That's it. No purchase necessary. Just "hi, may I have a free comic book?" And since you are there, browse around and see if something else interests you.
So fly, don't run or walk, fly to the nearest comic book store and claim your own. [Free Comic Book Day]