Display Featured Thumb In Post for Specific Category

Hi all, this is my first time on here, so I hope I don’t make a fool of myself! I’m not that familiar with PHP and WordPress’ definitions. Here’s what I want to do though:

Display the featured image of the post, in the post itself, for only posts in a certain category.

I figured it would be written out like so:

<?php
    if (in_category( 'news' )) {
      if ( has_post_thumbnail()){
        the_post_thumbnail();
    }
}
?>

I added it to my theme’s functions and it caused an error. Is the code wrong? Or did I just not place it in correctly?

The error message said “unexcepcted ‘>’ on line….”

p.s. I would preferably like to attach a class to the featured image that I can use to style it.