Use Themes
PowerPoint provides a variety of design themes, including coordinating color schemes, backgrounds, font styles, and placement of placeholders. Using pre-designed themes makes it easy for you to change the look of your presentation quickly.
Change Slide Size
1. Select any slide thumbnail of the presentation
2. From the Ribbon, click Themes tab > Page Setup > click Slide Size > choose a desire slide size that the presentation might be displayed on, or click on Page Setup to customize the size
Apply a Theme to a Presentation
1. Select any slide thumbnail of the presentation
2. From the Ribbon, click Themes tab > Themes > move the mouse pointer hover the any theme thumbnail in the Presentation Themes Gallery and click the 
to expand the gallery
3. Click on a desired theme to apply to all the slides in the presentation
Change the Color, Font or Effects of a Theme
1. From the Ribbon, click Themes tab > Themes Options
2. Do the following to change the color, font and effect scheme of a theme
- Click Colors button to change the color set
- Click Fonts button to change the font set
- Click Background button to change the background style set
Save a Custom Theme
A theme is a combination of one or more slide layouts with coordinating colors, a matching background, fonts, and effects. PowerPoint provides several standard themes. Find a standard theme that you like, and then modify it by changing the colors, fonts, or the background. You can then save the file as a custom theme. Once you create a custom theme in PowerPoint, you can use it in other Office applications
1. From the Ribbon, click Themes tab > Themes > click the down arrow on Save Themes button > choose Save Theme
2. Do the following:
- In the Save As box, type the name of the custom theme in the Save As box
- In Where list down arrow, choose My Themes folder
- In Format list down arrow, choose Office Theme (.thmx)
- Click Save button
3. The custom theme will display under Custom group in the Presentation Themes Gallery
