Classroom rules are an essential part of any class. They are the framework for behaviour and can allow the children to understand your expectations of them while in the classroom.
There are 12 classroom rules in this pack, but that may be too many to implement in one go. 4-5 focal rules at the start are the best way to introduce them, and you can add in more as the weeks go on and the children gain a better understanding of rules and their classroom responsibilities.
Having a visual for the rules makes them more real to the children and you can reference them on the wall at any stage, either to reinforce rules or to point out when a rule is broken.