Missing style.css

Hi all,

I apologize if this has already been covered, but I need help. I’m new to WordPress and very confused. We purchased a theme and went to install it on our GoDaddy WordPress administrative site, but I get the message below. Can you direct me as to how to fix this, and explain it like I’m five years old? Thanks!

The package could not be installed. The theme is missing the style.css stylesheet.