You might need to reset the administrator password for your website application especially if your website has been compromised.
Resetting the password will depend on your specific application, the reason that you need to change the password and how familiar you are with programming.
Please see the following table for links on how to reset/recover the admin password in the most common web applications:
WordPress | https://codex.wordpress.org/Resetting_Your_Password |
Joomla | https://docs.joomla.org/How_do_you_recover_your_admin_password |
Drupal | https://www.drupal.org/node/44164 |
If you are in any doubt and need further assistance please don't hesitate to open a support ticket and we will help you to reset the password for your web application.