Use a slide master to add consistency to your colors, fonts, headings, logos, and other styles, and to help unify the form of your presentation.
You can change a slide master's colors, fonts, or effects. You can hide or show placeholders.
Change the slide master
Select View > Slide Master.
Make the text, color, and alignment changes you want.
If you want to use a predefined theme, select that first by clicking Themes on the Slide Master tab. Then proceed with selecting Colors, Fonts, Effects, and Background Styles.
When you're done, select Close Master View.
Get more information
To learn about slide masters, see What is a slide master?
To add or change placeholders in a Master Layout, see Add a placeholder to a layout
To change text attributes, see Change text alignment, indentation, and spacing.
To use more than one slide master in a presentation, see Use multiple slide masters in one presentation