Missing CSS style

I am very new to this and am trying to install the Highend theme for the first time. I ended up with the following message. Is this an error on my part? Or is the “style.css stylesheet” actually missing from what I downloaded? If it is missing? How can I obtain it? Thank you!

Installing Theme from uploaded file: highend-ultimate-multi-purpose-wordpress-theme-theme-files.zip
Unpacking the package…
Installing the theme…
The package could not be installed. The theme is missing the style.css stylesheet.
Theme install failed.