The eCards UI theme requires eCards
4.0 or higher. Also, to avoid any PHP warnings and notices, PHP 5.6 is recommended, while PHP 7+ is optimal.
/wp-content/themes/directory or by using Appearance -> Themes -> Add New and upload your theme.
eCards UI featured customisable styles and can be edited from Appearance -> Customize -> eCards UI. Use the default colours or pick your own.
eCards UI does not use any separate shortcodes and inherits the eCards plugin ones.
Q: Can I use the theme without the plugin?