How to Modify the Master Slide in PowerPoint 2013
Open Slide Master View by opening the View tab on the Ribbon and then clicking the Slide Master button, found in the Master Views group.
Alternatively, you can hold down the Shift key and then click the Normal View button near the bottom right of the screen.
The Slide Master includes placeholders for three objects that appear at the bottom of each slide: the Date area, Footer area, and Number area.
A thumbnail of each Slide Master as well as the layouts for each Master are shown on the left side of the screen.