Login to your account at http://yourdomain.com/cpanel using your username and password. Yourdomain.com is your domain name.
In the top right corner of the cPanel window your username is visible. Click on it to see the drop down list of user preferences. Choose the Password & Security form the list.
In the new window type your current password in Old password field. Type your new password in the next field and retype to confirm it. Now press the change Password Now button.
Your password is successfully changed. You can also use the Password Generator button to create strong password.