These three buttons are
standard word processing buttons.
The new button 
allows you to start a new PowerPoint presentation file.
Alternatively, go to the File menu and highlight new, or press
zN.
The Open button 
will allow you to access an existing Powerpoint file and open it.
Alternatively, go to the File menu and highlight open, or press
zO.
To save your presentation,
press the save button 
and then specify the location where the presention is to be saved.
Alternatively, go to the File menu and highlight save, or press
zS.
