- Login into Plesk panel with Admin user (http://IP-address:8880).

- Click on Server from main navigation menu. This will open Tools & Settings page.

- Under Applications and Databases section, click on Database Servers link.

- Here, you will see list of installed database servers. Click on HostName for MS SQL Server.

- Click on Change Password option. Enter New Password, Confirm Password and click OK.

Following article will assist you to change password of MS SQL Server user 'SA' from Plesk Panel.