As Dinesh has said, you explain the organisation's Office Etiquette to new starters during their induction. It is not something you put on a form! In most cases this information is printed in the Employee Handbook, if the organisation has one.
If this is something that must be done, then print the Office Etiquette rules on a separate sheet of paper and attach to the form.
By the way, what is a "Joining Form?" Is this something the employee keeps? If not, then putting the rules on it is a pointless exercise! How can they read it in future if they don't have a copy?
I suggest you rethink this, and then try to have a rational discussion with your boss about doing things the right way.
By the way, how were the existing employees told about the rules? And more importantly, are they being followed. You cannot have rules for some, and not others.
By the way, the word is PLEASE, not plz. We encourage members to use correct English, and not sms speak. It helps those who are not as familiar with the English language to improve their knowledge.