Go to admin panel of your website, the URL should contain /wp-admin, then please login.
On the left side click plugins, then click Add plugin at the top, you should be seeing this:
Search WP post page clone, See the arrow at the bottom in red, on that click Install Now button and once done, click Activate:
You right now must be on the plugin page that your plugin is active. Please click on Pages or Posts, and any existing post click “Click to clone” see the arrow in red: