I am perfectly comfortable with presenting in front of huge numbers of people. It's the one thing I am quite good at, and can speak for hours if you let me. Suppose growing up and performing music and then presenting your design ideas in uni have helped.
Best piece of advice: make it so you are having a conversation with them. Just pick out a couple people and talk to them directly. I hate presentations where it sounds like they are reading off their cards or off the powerpoint they just put up. It sounds stilted and audience don't really like to be talked at. For practice I suggest reading a story to your siblings or nephew or neighbours kids, then when comfortable with that make the story up in your head on the go. This helps you to string ideas and words together on a whim, animate your voice and project it, create connections with your audience and loads of other benefits. Also shoulders back, back straight, chin up and smile.