To change your domain password:
1) Log into your Cpanel.
2) Select the "server" menu.
3) Select the "domain password" link from the left hand menu.
4) Click on the Change Password button on the home page.
5) Enter your current password in the Old Password field.
6) Enter your new password in the New Password and New Password (again) fields.
7) Click on the Change your password now! button. Your password has now been changed.