Here’s how it works, according to Chick-fil-A:

Make or buy your cow costume (or any sort of cow apparel, really).
Wear your cow costume to your favorite Chick-fil-A between Opening and 7 p.m.
Receive a free entree! (Free entrées for Cow Appreciation Day cannot be redeemed with the Chick-fil-A App.)
For costume ideas, you can check out Chick-fil-A’s collection of photos from previous Cow Appreciation Days.