You can open an existing presentation in several different ways:
Select More Presentations in the Open a Presentation section of the New Presentation task pane. If this pane doesn't appear, select File, New.
You can also open directly one of the previous four PowerPoint files you used by selecting it at the top of the Open a Presentation section of the New Presentation task pane. The File menu also displays these files at the end of the list of menu options.
Click the Open button on the Standard toolbar.
Press Ctrl+O from within PowerPoint.
Choose File, Open from the menu within PowerPoint.
You can also double-click ...