Adding co-authors

Hello wordpress forum

I am new user to wordpress, and are currently trying to make the co author plugin work on my wordpress webpage. I’ve installed co-authors and a tool called code snippets.
I’ve seen post saying that I need to locate the_author_post_link and replace the code with
if ( function_exists( ‘coauthors_posts_links’ ) ) {
coauthors_posts_links();
} else {
the_author_posts_link();
}

Where exactly do I find this code? Keep in mind I’m very new to this program, and have only been doing design to the webpage so far.
I’ve made a new snippet called co-authors and written the code there, not sure that is how its supposed to be done…
Can anyone guide me through this?

Kind regards