Yes, you have to edit the functions.php file of your theme.
Try to find a [themename]_setup function (according to WordPress code conventions) inside the functions.php file of your active theme and add the following code in it:
add_theme_support( 'automatic-feed-links' );
This code will add the RSS feed links to HTML <head> of all pages.
You can find more information here:
https://codex.wordpress.org/Automatic_Feed_Links