The demo is already imported.

When you purchase a theme from ThemeForest that bundles WPBakery Page Builder (formerly Visual Composer) and Slider Revolution, you are free to use these Premium plugins with the theme. However, your theme purchase does not give you individual WPBakery Page Builder and Slider Revolution licenses that allow you to activate or download these plugins as you wish. Activation doesn’t mean the plugin will not work but only that you cannot receive direct updates. Please don’t worry if you see warning messages about the plugin license activation.
You can use these plugins with our theme and you are fully compliant with the Envato’s policy, but you cannot activate them as the owner (so don’t try to use the theme purchase code to activate one of these plugins).