If you need to create multiple presentations with same theme, it’d be better to choose a theme and make it default, PowerPoint 2010 offers a simple way to let you set a default theme. Lets see how to do it.
To set a theme as default, launch PowerPoint 2010 and head over to Design tab, under Themes section, right-click the desired theme and select Set as Default Theme.
This will set the selected theme as default. On launching PowerPoint 2010 next time, you will see the selected theme already applied on the presentation slide.