Warnings or Infractions are handed out by the moderators in response to breaches of the forum rules or ettiqute. If you receive one of these, your best bet is to stop the behaviour that led to the infraction. Arguing with the moderator who issued the infraction, or trying to justify the behaviour that led to the infraction will not help your case and may lead to further infractions. Explaining that you were not aware that your behaviour was against the forum rules (perhaps because you have not read them) is not going to be a good use of your time. If you believe, however, that a misunderstanding has occurred you can send a polite private message to the moderator who issued your infraction, and the decision may be reviewed.
Please remember that their decision is final.
Not knowing the forum rules is not a defence, you agreed to them when you signed up.