For anyone reading this down the road, I found the Demo Content Importer by using the WordPress->Install Plugins->Install link under Demo Content Importer. That led to a 403 message, so I looked at the link itself and found the location that link was trying to open, which in this case was:
cardinal.swiftideas.com%2Fextras%2Fplugins%2Fcardinal-importer.zip
replaced %2F with / and got
cardinal.swiftideas.com/extras/plugins/cardinal-importer.zip
which let me download the .zip, which I then uploaded via WordPress->Plugins->Add new. Hopefully this got the right file to the right place, so far it looks ok.
I’m not sure why this .zip wasn’t in the original Cardinal master files I downloaded via ThemeForest. Hopefully this helps. Looking forward to putting the theme to work!