How to add subtitles

Hello,

I'm using this plugin to add subtitles: https://wordpress.org/plugins/kia-subtitle/
But I am a little lost on how to make them display? I've read a few posts but must be missing something.
I have added this code: if( function_exists( 'the_subtitle' ) ) the_subtitle(); via a hook element using the hook generate after entry title, but nothing is displaying. What am I missing?

Thank you for your help,
Dave

SOLVED, manged to get it working with shortcode in the block elements :)