Lots f practice makes an expert out of a novice. Also, prepare well. Preparation is the best lead to confidence.
Try this: grab the very first chance of speaking to a large audience about a topic you know “nobody else” can speak about better than you. It could be anything not necessarily related to the kind of topics you’re often afraid of addressing in a public large meeting of people, like a hobby or a favorite book, movie or even a personal story or an anecdote.
Once you get over the obstacles related to being in front of a large audience, you can concentrate on further refining your subjective public speech and presentation skills. Like the ones explained in the video, below: