To change the password for the database user,please follow the following steps :-
1) Login to Plesk control panel.
2) Click on "Subscriptinos" and then Click on "Manage Hosting" in front of the domain whose change the Database user password
3) Click on "WebSites and Domains".
4) Click on "Databases".
5) Click on "Database Name".
6) Click on "Database User" for whose user password you wanrt to change.
7) Click on username whose password you want to change.
8) Enter the new password two times and click on "OK".
You password has been chnaged now.
