1. Login to Plesk admin panel, https://<IP or domain>:8443
2. Click on 'Domains' option in 'Hosting Services'.
3. Search for the domain you want to change login password. (Let it be example.com)
4. Login to Control Panel of the selected domain.
5. Select Account >> My Profile >> General
6. You can see the account name and an option to change password in 'Panel Preferences' in 'General' tab.
7. Enter a strong password there and Click on OK button to make the changes in effect.
8. Verify user name and password using the given link, https://example.com:8443
