There's no way to disable the default right-click action (context menu) in Semplice, though you can implement this functionality with a simple plugin: https://wordpress.org/plugins/wp-content-copy-protector/
In the WordPress dashboard, navigate to "Plugins". Click the "Add New" button. In the search field write "WP Content Copy Protection & No Right Click". Install and activate the plugin.
Done! Now, right-click will be disabled on your website.