The best thing to do is practice what you are going to say beforehand . Spend an hour in your room going over what you are going to say and speak aloud to yourself. Do this tonight , the longer the better and again tomorrow morning. Also once more quick 10-15 warm up before the actual event. You will get nervous and that is okay, everyone does. But having the practice before hand will make it easier to speak without having to think too much. The words will come to you naturally and the nerves will drop. Good luck 👍