After activating the plugin go to Dashboard->Envy Mega Menu->Settings
Here you can enable the mega menu for your site menu location.

After that, your selected menu location will display with the Envy Mega Menu design on your site.
After activating the plugin go to Dashboard->Envy Mega Menu->Settings
Here you can enable the mega menu for your site menu location.
After that, your selected menu location will display with the Envy Mega Menu design on your site.