Add Breadcrumb without a plugin

Hi,

I got hold of two sets of code to be added in two files (functions.php and header.php) for having breadcrumbs on my pages.

My website is https://www.medicaltourismco.com.

I am not sure in which file to call the breadcrumb function. The theme that I am using on my website has a top.php file which has been called in header.php. Whenever I try to call the function using <?php the_breadcrumb(); ?> my pages stop showing. Where should I call this function?