Force a user to use strong passwords in Paid Memberships Pro. This plugin checks for length, matching/containing username, lowercase/uppercase, numbers, and special characters

gistfile1.txt

<?php

/*
Plugin Name: PMPro Strong Passwords
Version: 0.1
Plugin URI: http://www.paidmembershipspro.com/wp/pmpro-customizations/
Description: Force users to submit strong passwords.
Version: .1
Author: Scott Sousa
Author URI: http://slocumstudio.com
*/

/**
 * This function checks to make sure the user has submitted a strong password
 * by checking for length, lowercase/uppercase, numbers, special characters, and matching username.
 */
add_filter( 'pmpro_registration_checks', 'pmpro_strong_password_check' );
function pmpro_strong_password_check( $pmpro_continue_registration ) {
  $username = $_REQUEST['username'];
	$password = $_REQUEST['password'];

	// Check for length (8 characters)
	if ( strlen( $password ) < 8 ) {
		pmpro_setMessage( 'Your password must be at least 8 characters long.', 'pmpro_error' );
		return false;
	}

	// Check for username match
	if ( $password == $username ) {
		pmpro_setMessage( 'Your password must not match your username.', 'pmpro_error' );
		return false;
	}

	// Check for containing username
	if ( strpos( $password, $username ) !== false ) {
		pmpro_setMessage( 'Your password must not contain your username.', 'pmpro_error' );
		return false;
	}

	// Check for lowercase
	if ( ! preg_match( '/[a-z]/', $password ) ) {
		pmpro_setMessage( 'Your password must contain at least 1 lowercase letter.', 'pmpro_error' );
		return false;
	}

	// Check for uppercase
	if ( ! preg_match( '/[A-Z]/', $password ) ) {
		pmpro_setMessage( 'Your password must contain at least 1 uppercase letter.', 'pmpro_error' );
		return false;
	}

	// Check for numbers
	if ( ! preg_match( '/[0-9]/', $password ) ) {
		pmpro_setMessage( 'Your password must contain at least 1 number.', 'pmpro_error' );
		return false;
	}

	// Check for special characters
	if ( ! preg_match( '/[\W]/', $password ) ) {
		pmpro_setMessage( 'Your password must contain at least 1 special character.', 'pmpro_error' );
		return false;
	}

	// If we've passed all of the above, return the current continue registration flag.
	return $pmpro_continue_registration;
}

Hi..

As described, this fits exactly what I wanted to do with Paid Memberships Pro on my WP site.
But, I only have a basic understanding of how these things work...
To be more precise ...I don't know how to use the above file so it will work with the plugin and the theme I am using.

Could you please advice on how to implement the above code?

Kind thanks,

Vas