How do I install a Theme in Keynote?
When you open a template or a common keynote file, you can use the option File → Save theme... This puts your file in the necessary directory automatically and adds information about your theme to the welcome screen.
Typically they should be in:
~/Library/Application Support/iWork/Keynote/Themes/
You can copy yours there and they should show up; or when choosing a theme you can add them by navigating to the folder yours are in:
