Simple, you have to give a sentance in code possible to crack pluse a hint, the next person must crack it and give a code of thier own. Dont worry about spelling mistakes, its not easy to write coded sentances.
i'll start.
R szev gl nzmb xzivxgvih lm nb zxxlfmg! ( hint: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z backwards )