If you don’t like the slide layout you applied to a slide—or you selected the wrong layout—you can apply a new layout easily.
Click the Home tab.
Click the Layout button.
Select a slide layout from the gallery.
PowerPoint applies the new layout to your slide.
Tip
Slide Size In addition to changing the slide layout, you can also change the slide size. In PowerPoint 2013, the default slide size is now widescreen (16:9) to match the dimensions of most computers and projectors. If you prefer, you can change your slide size to the former default (4:3) by clicking the Slide Size button on the Design tab.