You can not learn to tango by reading a book. Public speaking is a physical activity. Stage fright is an emotional reaction which restricts physical abilities. To unlearn the unwanted physical reactions associated with stage fright, you must practice performance before an audience. Once it not enough.
Mastery requires distributed and incremental learning.
For these reasons, I recommend joining Toastmasters. Other options are to engage a professional coach or enroll in a class or seminar. Locate them on the Web. According to research on muscle memory reported in a recent issue of Swim Magazine , it takes up to six hours to move the memory of a new physical skill to a permanent storage site in the brain. This is for non-emotionally charged physical skills.