I am so nervous!

You can learn doing this with a coach.

You need to learn the skills of how to communicate effectively on a one to one basis which is I am sure you are already doing it with your close friends, classmates and family members. The frame of mind where you want to communicate your thoughts and needs are relatively the same as you speak in front of a group of people where even when you are on a one to one situation the attention will be on you when it is your turn to speak. In a group you do not have to be responsible for how people would react or understand as long as you had prepared your speech with careful constructive words to incur the right frame of thoughts. Just follow your prepared script and be done with it. Also, when you face the crowd it is a good advice that you pick out a particularly pleasant person among the audience and focus your attention on him or her to help you ease your tension by pretending that you are only speaking to this person. I hope these will be of help to you.