How to Add your own shortcode in Wordpress

In your "functions.php" file in your child theme folder create a function and use the following code to initiate the short code

add_shortcode('credits', 'show_website_credits');

The first variable above is the shortcode itself ( in this case [credits]) and the second variable is the name of the function.

In total it will look like this

function show_website_credits() {
  return "Website developed by Brendan.";
}
add_shortcode('credits', 'show_website_credits');