When I try to install the Newspaper theme I get this message “The package could not be installed. The theme is missing the style.css stylesheet. Theme install failed.”
Avoid duplicate thread. Check answer here -> Missing css stylesheet and archive already mounted
Checkout this guide (https://envato.com/blog/install-themeforest-wordpress-theme/) - sounds like you might have tried to install the full theme & docs download instead of just the theme zip file.