You need to install and activate Powerkit to make this feature work.
Enjoy the Subscription Form ???? shortcode integrated with your theme and Powerkit. Check the source code of the page in the WordPress editor (make sure you use the Text tab of the editor). Or, refer to the Opt-In Forms documentation.
[powerkit_subscription_form title=”Subscribe to Our Newsletter” text=”Subscribe today and receive daily promotions. No spam.”]