PowerPoint begins presentation design with a default theme. You can change the default to a pre-existing theme or one that has been created for your company or group. Once you change the default theme, all new presentations will automatically begin the design process with the new look.
1. Go to the Ribbon and select the Design tab.
2. In the Themes section, find the dropdown arrow located in the lower right corner and click it.
3. All available themes will be shown, you can also click Browse for themes to locate your custom theme.
4. Right-click on the chosen theme and select Set as Default Theme.
