Super simple: just vote on your favorite movies in “bracket” style and see how your “picks” do. If you complete your “bracket” you get a code for a free rental. The votes are held daily, but you can vote on what you miss if you don’t check it daily.
You can take care of all these shenanigans over at the Redbox Facebook page. Enjoy your free movie rentals (you should rent The Sessions and tell me how it is)!