1.3.0 not installing under MacOS 11.6

[brettcoryell]

I'm a little new to MacOS so apologies if this is dead simple.

I've downloaded ZotHero-1.3.0.alfred4workflow but when I double-click on it, I get an error message saying "There is no application set to open the document "ZotHero-01.3.0.alfred4workflow"

I am then invited to search the App Store or Choose an Application. I thought maybe I could choose Alfred, but it's grayed out in the Finder menu.