How the heck do I install a purchased keynote theme?

I purchased the theme
I unzipped the theme
I can open the .key file in keynote and see it working - I see all the slides for the template
But I can’t add it to the theme chooser. When I try ‘save theme’ and it it to theme chooser it just adds the generic theme instead of the purchased theme
I google and I get the advice to save it int he iworks folder, but there is no iworks folder.

How the heck are we meant to install these purchases into the chooser?

Thanks!

Did you ever figure this out? Same problem here… I don’t remember this being an issue on previous Keynote versions. Tx!

Same problem here