There are three good ways to improve your communication skills: practice, practice and practice! Take the opportunities you get to speak infront of an audience, you have to dare try different techninques to become more skillful!
Think through what you want to say and how you want to say it. Find pictures and enticings facts about the subject that you think can interest your audience. Learn how much about the subject the audience already know. Create your presentation with a common thread throughout the entire presentation. Build your material with an introduction, a main part and an ending. Test your presentation in front of an mirror or a friend. Check if the presention is within the time limit and if your message came through clearly. Revise if needed.
"Nothing demands as much preperations as an improvised speech." - Winston Churchill 1874-1965
When it is time to give your presentation it is good to get to know the room and the technical aides you will be using. Do you need to use a microphone? Can the audience in the back see/read everything you show?
Be yourself when you give a presentation! Use word that comes naturally to you and try to find your own style. Use energy, your personal engagement and presence.
Make the audience and your message the center of the presentation! Remember that every presentation is for the audience.
"Obscure speech gives obscure thoughts" - Esaias Tegner 1782-1846 (freely translated)
When you have given your presentation it is of value to reflect on what you have done. What went well and what can be improved for next time? You get valuable help here from your audience and teacher. Use their opinions and feedback and write them as well as your own into the self evaluation form so that you can remember them at your next presentation.