Honestly the main thing I have learnt about public speaking from experience is that you need to believe in yourself and really fake it till you make it.
You need to be prepared to speak in a fluid manner and act confident and that comes with just doing it (practice).
I would say watch a few YouTube videos on how to improve your public speaking and just try to practice in front of someone i.e. your friends / parents / anyone you trust (just talk about something that interests you) or even talk in front of a mirror or video yourself. Afterwards, always reflect on what you could have done better e.g. your confidence, body language, talking clearly, understanding your audience (not making things too complicated) etc.
Even if it goes bad, they are people too and it wont matter in the grand scheme of things and remember you got this.
Hope this helped.