A powerful presentation has certain elements that set it apart from a so-so presentation. This article in the Harvard Business Review concisely discusses these elements.
Of course, for an opportunity to practice public speaking, learn from constructive feedback, improve your skills in a “grow-as-you-go” setting and eventually deliver powerful presentations, you can always find a local Toastmasters Club. Toastmasters is a worldwide organization that offers a proven system. Alternatively, you can hire a coach for a one-on-one experience.