Inside your Vantage MT4 platform, select Tools > Options, then select the Server tab and then Change.
Alternatively, you may right-click on the account under the Navigator tab to reset the password for your trading account. The trading account password can also be reset from within your client portal.
If you have forgotten your password, for security reasons, it can only be reset using your secure client portal. You can refer to your Live account section and click on the lock shaped icon to set a new password for your trading account. Once clicked, choose Forgot Password, and the instructions will be sent to you by email.
Please keep in mind that your password for MT4 is different to your client portal password.