Design themes make it easy to apply a set of coordinating features to each of your slides. The slide backgrounds and font styles, colors, and sizes are preserved in the design theme. By default, only one design theme can be applied to a presentation, but you can add one or more design themes to a presentation by adding them to the slide master, which contains all of the information about the slide layouts and styles in that presentation.

In the Master Views group, select Slide Master. The Slide Master tab appears on the ribbon.

Select the Master slide. This is the top slide in the Slide window.

In the Edit Theme group, select the Themes drop-down arrow. This displays the available design themes that can be applied to the presentation.