My Preferred Way to Change the WordPress Login URL

First, changing the login URL helps prevent brute-force attacks that could make the site inaccessible or drive up CDN traffic. It can also deter people who are just messing around. 1. Rename wp-login.php in the website’s root directory to wp-a.php (or another name; wp-a.php is used in this example), and replace every occurrence of wp-login.php in that file with wp-a.php; 2. Open wp-includes/general-template.php under the root directory. Leave the code at around line 438 unchanged:  

$login_url = site_url('wp-login.php', 'login');

Replace every other occurrence of wp-login.php in that file with wp-a.php. Once you have finished editing, save the changes over the original file. This changes the login URL.  

Reference article: https://devework.com/modify-wordpress-login-file.html