Post Pagination (Split Posts into Multiple Pages)

Hello there,

Post Pagination (post multiple pages) are not showing after the post content. Rather, are showing after the related posts. Is there anyways, that it can show after the post content?

Example post: http://thechoice.one/the-purpose-of-life-transcript/

Also, where is the location of “Single.php” file under theme to make changes to Page-Links tag (<?php wp_link_pages(); ?>)

Thanks,