Unable to access WordPress functions from functions.php


I am following a tutorial in an attempt to create a custom theme on WordPress. I created my functions.php file in my theme folder, and am attempting to use the WordPress function ‘wp_enqueue_style()’ from functions.php. ‘wp_enqueue_style()’ is not working or populating on my text-editor, in fact, none of the functions starting in ‘wp_’ are working in my functions.php.

I checked the source of the wp_enqueue_style() function, which is ‘includes/function.wp-styles’, and it IS included in my directory, and I also tried using require_once(‘path to includes/function.wp-styles’); to link to that file from within functions.php.

I am totally clueless at this point…thank you in advance for your help.