The difference from an appeal
You file an appeal against a judgment that has not entered into legal force. You file a cassation complaint, under article 403 of the Civil Procedure Code, against a judgment that has entered into legal force and was not heard on appeal. Both instances check the legality, the validity and the fairness of the judicial act, and both may examine new evidence.
What to stress in the complaint
State exactly what is wrong with the judgment: for example, which rule the court broke, and how that breach changed the outcome. The phrase "the court decided wrongly" is not enough.
The time limit
Under article 405¹ of the Civil Procedure Code, you file the cassation complaint within six months from the day the judgment of the first instance court enters into legal force. If you missed the time limit for a valid reason, file a motion to restore it. You must file the motion no later than three months from the day the six-month limit expired.
The result
The cassation instance may uphold the judgment without changes, amend it, or annul it and render a new judgment. On the grounds the law states, the court may annul the judgment and leave the application without consideration, or terminate the proceedings. If the case was heard in breach of the jurisdiction rules, the case materials go to the proper court.