installation of theme failed

Hello,
I bought the theme “XStore | Responsive Multi-Purpose WooCommerce WordPress Theme”
in its installation with wordpress I have the indication:
"Install a theme from a file: themeforest-9Z9YwJz8-xstore-responsive-woocommerce-theme.zip

Impossible to install the package. The theme is missing the style.css style sheet.

The installation of the theme failed. "

what can I do;