Under Orientation, click the orientation you want. To set the page orientation for all of the slides in your presentation, on the Slide Master tab, click Slide Size > Page Setup. To apply a design or theme-based colors, fonts, effects and backgrounds, see Create your own theme in PowerPoint. To remove any of the built-in slide layouts that accompany the default slide master, in the slide thumbnail pane, click each slide layout that you want to delete, and then on the Slide Master tab, click Delete.
To create one or more custom layouts or to modify existing layouts, see Apply or change a slide layout.
Note: In the slide thumbnail pane, the slide master is the larger slide image, and the associated layouts are positioned beneath the slide master.
