Adding PHP code and Header to Single Post pages

Hi, this should be my last question. Sorry for having so many. I want to add a string of php code to insert an author bio box in the single page blog page. I also want to add an <h3> header right above the social media icons on the single blog page.

This is the php code:
<?php if ( function_exists( 'wpsabox_author_box' ) ) echo wpsabox_author_box(); ?>