Public speaking can be tough if you are a naturally introverted person. Yale's psychological department was kind enough to give out tips for those who are intimidated by public speaking. Their first tip is to outline all the material fully and thoroughly without writing a speech word for word. Memorizing something word for word actually increases anxiety as it creates a pressure to be right each and every word that comes out of your mouth. Having an outline makes you fully aware of the movement your speech will take while taking off the pressure to say exactly the right thing.
The second is to keep a token of emotional security. Athlete's pre-game rituals are cited as inspiration and presenting is no different. Keeping a sentimental object to ground you will only enhance your confidence as it's something personal and familiar unlike the speech you are about to give.
Third, remember that your audience probably is not paying nearly as much attention to your speech as you think they are. Most are probably at least half distracted, they'll remember your tone and enthusiasm way more than they will the content of your speech itself.
Lastly, confidence is the currency of success when it comes to public speaking. The audience can tell if you are nervous and will be nervous in return if you act accordingly. Pretend you're confident even if you're freaking out inside, basically "fake it till you make it."
These tips are designed to outsmart your psychological processes that inhibit your public speaking. Use them and you'll be effective and persuasive!