When you add a slide, you choose among different slide layouts that are based on your presentation’s theme.
Do one of the following:
Select a slide in the slide navigator, then press Return or option-click 
in the toolbar to create another slide with the same layout.
Click in the toolbar, then select a slide layout.
To delete a slide, select the slide in the slide navigator, then press Delete. Shift-click to select multiple slides to delete.
If you added a slide to your presentation but want to try a different layout, you can quickly change its layout from the Format inspector.
Select the slide in the slide navigator.
In the Layout pane of the Format inspector, click Change Master.
Select a slide layout to apply it.
You can also add a Master item to the toolbar to quickly change slide layouts. To learn more about customizing the toolbar, see Customize the toolbar.
Select a slide in the slide navigator.
In the Format inspector, click the disclosure triangle next to Background.
Choose a fill type from pop-up menu.
Tip: Choose Color Fill for a single color.
The slide background fill choices is similar to a shape fill. To learn more about fills, see Change an object’s appearance.
Double-click placeholder text and type your own.
Do either of the following:
Drag an image from the Finder onto the placeholder image.
Click 
in the bottom-right corner of placeholder image, then select an image from your iPhoto, Aperture, or Photo Booth library.