Every theme in PowerPoint includes a set of slide layouts. A slide layout defines how text and other content is arranged on a slide. If the pre-designed layouts in a theme don't work for your slide show, you can change them.

Arrange slide content with different slide layouts to suit your taste and preference, or to improve the clarity and readability of the content.

1. Select the slide that you want to change the layout for.

2. Select Home > Layout.

3. Select the layout that you want.

   The layouts contain placeholders for text, videos, pictures, charts, shapes, clip art, a background, and more. The layouts also contain the formatting for those objects, like theme colors, fonts, and effects,.

   Note: Select Home > Reset if you made layout changes you don't like, and want to revert to the original layout. Using Reset doesn't delete any content you've added.

Source: Microsoft