Reusing your existing slides can be a great help: first you need not recreate stuff you already have and secondly you are saving so much time that you can use more effectively to practice your presentation!
Having said that, always start by creating an outline of your presentation. This is important because it gives you an opportunity to plan your slides all over again. Thereafter, reuse any existing slides. PowerPoint provides a quick command that locates specific slides, and enables you to add it to the active presentation. While this process works the same way in all versions of PowerPoint.
To learn more, choose your version of PowerPoint. If we do not have a tutorial for your version of PowerPoint, explore the version closest to the one you use.
Microsoft and the Office logo are trademarks or registered trademarks of Microsoft Corporation in the United States and/or other countries.