What do I do with these complete PowerPoint presentations?

Power Presentations > Pre-Sales Questions

The short answer is anything you want! 

Power Presentations are not locked, they are completely editable. You can open one and edit the text, swap out the images with your own, update the data in the charts to yours and use it as your own presentation.

 
You can also...
Copy entire slides to your own presentations.
Copy the contents of slides to your own presentations.
Copy select pieces off any slide to your own presentations.