To change password from your MetaTrader 4 Client Terminal, you must be logged into the trade account first.
From the top toolbar, click “Tools”, then click “Options” from the drop down list.
Enter your current password (old password), then your new password, then confirm your new password again, then press “OK”.
You should leave the radio box “Change master password” unless you know what you’re doing.
If your password is successfully changed, you should see the following message in your Journal tab of your terminal.
“master password changed, terminal will be reconnected”