Enqueue styles and scripts in Wordpress

simple-enqueue-styles-scripts-wordpress.php

<?php 
add_action( 'wp_enqueue_scripts', 'my_custom_enqueue' );
function my_custom_enqueue() {

	// Custom scipt
	------------------------//
		// Child theme's function.php
		wp_enqueue_script( 'custom-js', get_template_directory_uri() . '/path/to/script.js' );
		
		// In your plugin's function.php
		wp_enqueue_script( 'custom-js', plugin_dir_url( __FILE__ ) . '/path/to/script.js' );

	// Custom styles
	------------------------//
		// Child theme's function.php
		// Main stylesheet  
		wp_enqueue_style( 'custom-main-css', get_stylesheet_uri() . '/style.css'); );
		// Other stylesheets 
		wp_enqueue_style( 'custom-other-css', get_template_directory_uri() . '/path/to/custom-style.css' );

		
		// In your plugin's function.php
		wp_enqueue_style( 'custom-other-css',  plugin_dir_url( __FILE__ ) . '/path/to/custom-style.css' );
		
		
	// Custom Ajax
	------------------------//
		// Child theme's function.php
		wp_enqueue_script( 'custom-ajax-script', get_template_directory_uri() . '/path/to/my-ajax-script.js');
		wp_localize_script( 'custom-ajax-script', 'my_ajax_object',
				array( 'ajax_url' => admin_url( 'admin-ajax.php' ) ) );
				
		// In your plugin's function.php
		wp_enqueue_script( 'custom-ajax-script', plugin_dir_url( __FILE__ )) . '/path/to/my-ajax-script.js');
		wp_localize_script( 'custom-ajax-script', 'my_ajax_object',
				array( 'ajax_url' => admin_url( 'admin-ajax.php' ) ) );
				
				
	// Font awesome
	------------------------//
		// Directly from website. Updated version go to https://origin.fontawesome.com/start
		wp_enqueue_style('fa-custom-name', 'https://use.fontawesome.com/releases/v5.7.1/css/all.css'); 

		// OR

		// version hosted on Bootstrap CDN. (preferred) Updated version go to https://www.bootstrapcdn.com/fontawesome/
		wp_enqueue_style('fa-custom-name-bs', 'https://stackpath.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css');
}
?>