[Plugin: WP-Subtitle] Not appearing on Recent Posts?

I’m trying to get the WP-subtitle plugin to appear on my front page (i.e. recent posts) but it only shows on the main blog post page.

I’d throw the subtitle PHP function in the recent-page file if I knew what it is – but I haven’t the slightest clue. To get it appearing in the blog entry all I did was paste it in single.php under the title function.

If anyone can help that’d be great.

https://understandingteenagers.com.au/blog/ <– that’s the page I was it to appear on. I’ve looked in index.php but I can’t see a suitable place for it.