Hi Gregory… first, I’m here to help. Second, read this: https://www.styledthemes.com/help-faqs/140-the-stylesheet-is-missing-after-installing-the-theme
And third, I am guessing you did not unzip the downloaded file as the file is so named “unzip-first” in the file name, and the download page also states to unzip it first, but assuming you tried to install the first downloaded package? Inside that is the actual celestial.zip file that you install.
If however, you did all this and still end up with that message, contact me and I will be happy to install it for you.