It depends on what you are doing. There are 3 different types of actions. "Dispute" is the first, "Appeal" is the second, and "Counter-Notification" is the third. You have to dispute before you can appeal, and usually you have to do both of those before you can send a counter-notification. Do you have a claim that you are trying to dispute? Did you already dispute it and it got rejected and now you are trying to appeal it? Or did the video got taken down and you are wanting to send a counter-notification?
The text you send depends on the type of thing you are trying to do.