If you have a presentation on your computer that you have created with a 2010 theme, do the following:
Open the presentation
Select the Design tab
Click dropdown next to Themes and choose Save current theme, give an appropriate name
Your new theme will be automatically added to the following folder:
C:\All users\Name user\AppData\Roaming\Microsoft\Templates\Document Themes
From now on you can use it, click the Design tab, in the Themes group click the More button, you will find it under custom themes.
Alternative
Select the Design tab
Click dropdown next to Themes and choose Browse for Themes
Navigate to the presentation file and click Apply.
Click dropdown next to Themes and choose Save current theme, give an appropriate name
